EXHIBIT 2.2



                                 ATTACHMENT XIV




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                    STOCK PURCHASE AND SHAREHOLDER AGREEMENT


                                 By and Between


                                TOSCO CORPORATION


                                       and


                        UNION OIL COMPANY OF CALIFORNIA



                          ----------------------------

                          Dated as of January 15, 1997
                          ----------------------------










                    STOCK PURCHASE AND SHAREHOLDER AGREEMENT


     THIS STOCK PURCHASE AND SHAREHOLDER  AGREEMENT,  is dated as of January 15,
1997 ( "Agreement"),  between and among TOSCO CORPORATION,  a Nevada corporation
("Tosco"),  and  UNION OIL  COMPANY  OF  CALIFORNIA,  a  California  corporation
("Union").

                            RECITALS
                            --------

          WHEREAS,  Tosco  and  Union  have  entered  into a Sale  and  Purchase
Agreement for the business and assets of the 76 Products  Company dated December
14, 1996 ("Sale and Purchase Agreement"),  pursuant to which Tosco agreed to buy
and Union agreed to sell the business and assets that constitute the 76 Products
Company segment of Union ("76 Products' Business and Assets"); and

          WHEREAS,  the Sale and Purchase  Agreement  provides that a portion of
the  purchase  price for the 76 Products  Business  and Assets may be payable in
Common Stock of Tosco, $.75 par value; and

          WHEREAS,  Tosco and Union have entered into an Escrow  Agreement dated
January 15, 1997 ("Escrow  Agreement"),  and,  pursuant to the Sale and Purchase
Agreement, deposited this Agreement into escrow.

          NOW, THEREFORE, the parties agree as follows:

     1.  Definitions.  For all purposes of this  Agreement,  the following terms
shall have the following  meanings (such meanings to be equally  applied to both
the singular and plural forms of the terms defined); all terms of this Agreement
that are not defined specifically herein shall have the meaning assigned to them
in the Sale and Purchase Agreement:

          "Affiliate"  of any  specified  Person  shall  mean any  other  Person
directly or indirectly  controlling or controlled by or under direct or indirect
common control with such specified Person.

          "Agreement" shall have the meaning set forth in the preamble hereof.

          "Board" shall mean the board of directors of Tosco.

          "Business  Day" shall mean a day,  other than a Saturday  or a Sunday,
when commercial banks are open for business in Los Angeles,  California, and New
York City, New York.

                                       1



          "Closing"  shall have that  meaning set forth in Section  10(a) of the
Sale and Purchase Agreement.

          "Common Stock" shall mean the shares of Tosco common stock,  par value
of $.75, delivered to Union pursuant to Section 2 of this Agreement and which at
the relevant date is beneficially  owned by Union or an Affiliate of Union,  and
all shares of such common  stock  issued  pursuant to a stock  split,  dividend,
reorganization, reclassification, or recapitalization of such common stock.

          "Derivative Security" shall mean a security issued by Union or any one
or more of its Affiliates which is convertible,  exchangeable or exercisable for
Common Stock.

          "Escrow  Account"  shall have the meaning set forth in Section 3(b) of
the Escrow Agreement.

          "Escrow Agent" shall have the meaning set forth in the Preamble of the
Escrow Agreement.

          "Exchange  Act" shall mean the  Securities  Exchange  Act of 1934,  as
amended.  Each  reference to the Exchange  Act or a rule or  regulation  adopted
under the Exchange Act shall mean the Exchange Act or the rule or  regulation as
in effect at the time for application of a provision of this Agreement.

          "Market  Price"  shall mean the  average of the daily  averages of the
high and low trading prices for Purchaser  common stock reported on the New York
Stock  Exchange  Composite  tape for the ten business days preceding the Closing
Date,  but in no case less than $45 per share unless Tosco elects,  by execution
and delivery of Supplement No. 1 attached to this Agreement, to issue sufficient
shares  of Common  Stock  such  that the  Market  Value is equal to (i) the Base
Purchase  Price  pursuant to Section  3(a) of the Sale and  Purchase  Agreement,
minus (ii) the fair market value of the cash and  marketable  securities  (other
than the right to receive  Common  Stock) in the Escrow  Account on the  Closing
Date.

          "Market Value" shall mean the Market Price multiplied by the number of
shares of Common Stock to be delivered.

          "Person"  shall  mean  any  corporation,  limited  liability  company,
natural  person,  firm,  joint  venture,   partnership,   trust,  unincorporated
organization,  enterprise,  other legal entity,  government or any department or
agency of any government.

          "Securities  Act" shall mean the  Securities  Act of 1933, as amended.
Each reference to the  Securities Act or a rule or regulation  adopted under the
Securities  Act shall mean the  Securities  Act or the rule or  regulation as in
effect at the time for application of a provision of this Agreement.

                                       2


          "Shareholder" shall mean any holder of shares of Common Stock.

     2.   Purchase and Sale. At Closing, Tosco will deliver to Union, as partial
          -----------------

consideration, a number of shares of Common Stock, to be determined as follows:

          The number of shares shall equal:

               (a) the Base Purchase  Price pursuant to Section 3(a) of the Sale
               and Purchase  Agreement,  minus the fair market value of cash and
               marketable  securities  (other  than the right to receive  Common
               Stock) in the Escrow Account on the Closing Date,

               Divided by

               (b) the Market Price.

     3.   Representations and Warranties of Union.
          --------------------------------------- 

          (a) Union (i) is a qualified  institutional  buyer, (ii) is aware that
the sale of the Common  Stock to it is being made in reliance  upon an exemption
to  registration  under the  Securities  Act, and (iii) is acquiring such Common
Stock for its own account;

          (b) Union  understands  that the Common Stock has not been  registered
under the Securities Act and may not be reoffered,  resold, pledged or otherwise
transferred by Union except (a)(i) to a person who Union reasonably  believes is
a qualified institutional buyer acquiring for its own account or for the account
of a qualified  institutional buyer in a transaction meeting the requirements of
Rule  144A  under  the  Securities  Act,  (ii)  pursuant  to an  exemption  from
registration  under  the  Securities  Act,  (iii)  in  an  offshore  transaction
complying with Rule 903 or Rule 904 of Regulation S under the Securities Act; or
(iv) in a transaction registered under the Securities Act, and (b) in accordance
with all applicable securities laws of the states of the United States and other
jurisdictions;

          (c) The certificates  evidencing the Common Stock will bear legends to
the following  effect,  unless Tosco  determines  otherwise in  compliance  with
applicable law:

          (i) "THE COMMON STOCK EVIDENCED  HEREBY HAS NOT BEEN REGISTERED  UNDER
          THE U.S. SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT") AND
          MAY NOT BE OFFERED,  SOLD,  PLEDGED OR  OTHERWISE  TRANSFERRED  EXCEPT
          (A)(i)  TO A PERSON  WHO  UNION  REASONABLY  BELIEVES  IS A  QUALIFIED
          INSTITUTIONAL  BUYER  ACQUIRING FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT
          OF A  QUALIFIED  INSTITUTIONAL  BUYER  IN A  TRANSACTION  MEETING  THE
          REQUIREMENTS  OF RULE 144A UNDER THE SECURITIES  ACT, (ii) PURSUANT TO
         

                                       3


          AN EXEMPTION FROM  REGISTRATION  UNDER THE SECURITIES ACT, (iii) IN AN
          OFFSHORE TRANSACTION COMPLYING WITH RULE 903 OR RULE 904 OF REGULATION
          S UNDER THE SECURITIES ACT; OR (iv) IN A TRANSACTION  REGISTERED UNDER
          THE  SECURITIES  ACT,  AND  (B)  IN  ACCORDANCE  WITH  ALL  APPLICABLE
          SECURITIES  LAWS  OF  THE  STATES  OF  THE  UNITED  STATES  AND  OTHER
          JURISDICTIONS."

          (ii) "THE SHARES  EVIDENCED HEREBY ARE SUBJECT TO A STOCK PURCHASE AND
          SHAREHOLDERS   AGREEMENT,   DATED  AS  OF   JANUARY   15,   1997  (THE
          "SHAREHOLDERS AGREEMENT", A COPY OF WHICH MAY BE OBTAINED FROM TOSCO),
          THE SHARES ARE  TRANSFERRABLE  ONLY IN ACCORD  WITH AND SUBJECT TO THE
          CONDITIONS OF THE  SHAREHOLDERS  AGREEMENT,  AND, ONCE  TRANSFERRED BY
          UNION TO ANY PERSON, NOT AN AFFILIATE OF UNION, OWNING LESS THAN 5% OF
          TOSCO'S  COMMON  STOCK  AFTER THE  TRANSFER,  ARE NOT  SUBJECT  TO THE
          SHAREHOLDERS AGREEMENT."

     4.   Covenants of Union.  Union agrees as follows:
          ------------------

          (a) Promise to Liquidate. Union shall undertake to sell, distribute or
              --------------------
otherwise  dispose of the Common Stock as soon as reasonably  practical in light
of  market  conditions  so as to  maximize  the  price  received  by Union  upon
disposition  of all of the  Common  Stock.  In making its  decisions  concerning
timing and method of any disposition of Common Stock, Union shall consult with a
nationally  recognized investment banking firm and be fully protected in relying
on the advice of any such firm.

          (b) Share  Voting.  Union  shall  arrange  for the Common  Stock to be
              -------------
present  at all  shareholders'  meetings  of Tosco and shall  vote its shares in
proportion,  for,  against  and  in  abstention,  to  the  votes  of  the  other
shareholders  present at such meeting,  if the vote relates to a matter on which
the interest of Union and the interests of the other shareholders are reasonably
similar.  If any Person solicits written consent for action from shareholders of
Tosco,  Union shall deliver to the Person  soliciting  such  consent,  a written
consent  which  shall,  at a time that the written  consent  becomes  effective,
consents to the action by a percentage  of the Common Stock that is equal to the
percentage by which all other shares, not held by Union consented to the action.

          (c) Standstill Provision.  Union shall not acquire any common stock of
              --------------------
Tosco or  securities  convertible  into  common  stock of Tosco nor shall  Union
propose  to  Tosco  or  any  Person  any  acquisition   transaction   (excluding
transactions in the ordinary course of business of the type previously conducted
by Union and Tosco)  between Union and Tosco and/or the Tosco  security  holders
involving any of their  respective  securities or assets unless Tosco shall have
requested in writing that Union make such a proposal.

                                       4


          (d) Passivity Provision. Union shall not, directly or indirectly:
              -------------------

     (i) seek representation on or seek to influence Tosco's Board of Directors;

     (ii) solicit or participate in soliciting proxies or actions by
written  consent with respect to any matter  presented  to the  shareholders  of
Tosco;

     (iii) encourage any third party to seek control of Tosco;
               

     (iv) propose a slate of directors  in  opposition  to any slate of nominees
proposed by management or the Board of Directors of Tosco; or

     (v)  without  consent of Tosco,  sell  Common  Stock to anyone  who,  after
completion of such sale, would own more than 5% of the common stock outstanding,
except in the case of sale into a public tender offer  available to shareholders
generally and except a sale to underwriters  who purchase in the ordinary course
of their  business  with a view toward  subsequent  resale (other than resale to
anyone who such underwriter knows, after completion of such sale, would own more
than 5% of the common stock outstanding).

     5.   Covenants of Tosco.  Tosco agrees as follows:
          ------------------

     (a) Share Listing.  Tosco shall list the Common Stock on the New York Stock
         -------------
Exchange.

     (b) Best  Efforts.  Tosco shall use its best efforts to obtain  shareholder
         -------------
approval for the issuance of Common Stock.

     (c) Accountant's Letters. Tosco shall deliver(i) to Union at Closing a
         --------------------
letter from Tosco's  independent  public  accountants which shall be in the form
permitted by Statement on Auditing Standards No. 75, and (ii) to each person who
would be entitled to receive,  and who requests,  a comfort  letter  pursuant to
Statement  on  Auditing  Standards  Nos.  72 and 76 at the  closing of any other
transaction in Common Stock, in each case applying procedures no more burdensome
than those  described  in the form of comfort  letter  customarily  delivered by
Tosco's  independent public  accountants in connection with underwritten  public
offerings of Tosco common stock.

     (d) Sale or Disposition of Common Stock.  Tosco acknowledges that Union may
         -----------------------------------
dispose of Common  Stock in one or more of several  methods,  including  but not
limited to: (i) a registered offering of Common Stock or Derivative  Securities;
(ii) an offering of Common Stock or Derivative Securities under Rule 144A of the
Securities Act; (iii) an offering of Common Stock or Derivative Securities under
Regulation S of the Securities  Act; or (iv) a  distribution  of Common Stock to
shareholders  of Union  and its  Affiliates  in a  transaction  which is  either
required  to  be  registered   under  the  Securities  Act  or  is  exempt  from

                                       5


registration  under the Securities Act. Tosco shall do all things  reasonable or
beneficial in order to assist Union in selling or disposing of the Common Stock,
including the following:

               (i) If Union has sold Common Stock or  Derivative  Securities  in
reliance on a private placement exemption, Tosco agrees that it will not solicit
any  offer  to buy or offer  to sell  the  Common  Stock by means of any form of
general  solicitation  or general  advertising (as defined in Regulation D under
the  Securities  Act) or in any manner  involving a public  offering  within the
meaning of 4(2) of the Securities Act ;

               (ii) Tosco shall not engage in any directed  selling efforts with
respect  to the  Common  Stock  within the  meaning  of  Regulation  S under the
Securities  Act and  Tosco and each  such  person  acting on behalf of Tosco has
complied  and  will  comply  with  the  offering  restrictions   requirement  of
Regulation S;

               (iii) If  Union  sells  Derivative  Securities  in a  transaction
exempt from  registration  pursuant to Rule 144A under the Securities  Act, then
during the three year period following the last closing date of a sale by Union,
Tosco shall make available,  if it is not then subject to Section 13 or 15(d) of
the Exchange Act, upon request,  to any seller of the Common Stock or Derivative
Securities,  the information concerning Tosco specified in Rule 144A(d)(4) under
the Securities Act, (so long as such requirement is necessary in order to permit
holders of the Common Stock or  Derivative  Securities  to effect  resales under
Rule 144A); and

               (iv) Tosco  shall not sell,  offer for sale or solicit  offers to
buy or  otherwise  negotiate  in  respect  of any  security  (as  defined in the
Securities  Act) which could be integrated  with the sale of the Common Stock or
any Derivative  Security in a manner which would require the registration of the
Common Stock or any Derivative Security under the Securities Act.

          (e) Standstill Provision.  Tosco shall not acquire any common stock of
              --------------------
Unocal Corporation,  a Delaware corporation and holder of all of the outstanding
stock of Union ("Unocal"), or securities convertible into common stock of Unocal
nor shall  Tosco  propose to Unocal or any Person  any  acquisition  transaction
(excluding  transactions  in  the  ordinary  course  of  business  of  the  type
previously  conducted by Union and Tosco)  between Unocal and Tosco and/or their
security holders  involving any of their respective  securities or assets unless
Union shall have requested in writing that Tosco make such a proposal.

          (f) Conflict with Articles or Bylaws. Tosco agrees that if any term or
              --------------------------------
provision of this  Agreement is  inconsistent  or in conflict with the terms and
provisions of its Articles of  Incorporation  or Bylaws,  as may be amended from
time to time,  Tosco  shall  abide by the terms and  provisions  hereof  and, if
necessary, to the extent within its control, cause the conflicting provisions in
the Articles or Bylaws to be amended accordingly.

                                       6


     6.   Grant of Registration Rights.
          ----------------------------

          (a) Union is  entitled  to  demand  registration  of Common  Stock for
aggregate  proceeds of a minimum of $200  million  per  demand,  except if Union
possesses less than a $200 million value of Common Stock in which case Union may
demand registration of its remaining balance of Common Stock, but, in any event,
Union is entitled to not less than two demand registrations. Notwithstanding the
foregoing:

               (i) If Tosco shall furnish to Union,  upon Union's  request for a
demand registration,  a certificate signed by the Chairman of the Board of Tosco
stating that in the good faith  judgment of the Board of Directors,  it would be
seriously  detrimental  to an  equity  or debt  offering  by Tosco or any  other
corporate  transaction  by  Tosco,  in  either  case for  which  Tosco  had made
substantial  preparation  before  the date of receipt  of  Union's  request  for
registration pursuant to this Section and it is therefore essential to defer the
filing of such registration statement,  Tosco shall have the right to defer such
filing for the minimum  period of time  necessary to eliminate  the detriment to
Tosco,  provided  however that each such  deferral  shall not exceed a period of
more than  ninety  (90) days and all such  deferrals  in any  twelve  (12) month
period shall not exceed one hundred and twenty (120) days; and

               (ii) Tosco shall not be required to make a registration statement
effective  with the SEC  pursuant to a demand  registration  by Union within one
hundred  and  eighty  (180)  days  of the  effective  date  of the  registration
statement relating to a previous demand.

          (b) If Tosco  proposes to file any  registration  relating to a public
equity offering solely for cash, Tosco shall, at such time,  promptly give Union
written  notice of such  registration.  Upon the written  request of Union given
within twenty (20) days after mailing of such notice by Tosco, Tosco shall cause
to be registered under the Securities Act all of the Common Stock that Union has
requested to be registered  unless the registration  statement relates to a firm
commitment underwriting arrangement.  In that case, Tosco shall consult with the
managing  underwriters  and Union and shall use its best  efforts to include the
shares of Common Stock requested to be registered by Union.

     7. Mechanical Provisions.  (a) Whenever required to effect the registration
        ---------------------
of any Common Stock, Tosco shall:

               (i) Prepare and file with the SEC a  registration  statement,  as
expeditiously as reasonably  possible,  and in any case within twenty (20) days,
with  respect  to such  Common  Stock  and use its best  efforts  to cause  such
registration statement to become effective, and, upon the request of Union, keep
such registration  statement effective for up to ninety (90) days, unless in the
reasonable  opinion of counsel to Union,  some  longer  period is  necessary  to
effect the method of distribution  of the Common Stock or Derivative  Securities
selected by Union;

                                       7


               (ii) Prepare and file with the SEC such amendments and
supplements to such registration statement and the prospectus used in connection
with  such  registration  statement  as may be  necessary  to  comply  with  the
provisions  of  the  Securities  Act  with  respect  to the  disposition  of all
securities covered by such registration statement;

               (iii)  Furnish to Union such  numbers of copies of a  prospectus,
including a preliminary  prospectus,  in conformity with the requirements of the
Securities Act, and such other documents as they may reasonably request in order
to facilitate the disposition of Common Stock owned by them;

               (iv) Use its best efforts to register and qualify the  securities
covered by such  registration  statement under such other securities or Blue Sky
laws of such jurisdictions as shall be reasonably  requested by Union,  provided
that Tosco  shall not be  required  in  connection  therewith  or as a condition
thereto to qualify to do business or,  except as required  under the  Securities
Act,  to file a general  consent to  service  of  process in any such  states or
jurisdictions;

               (v) In the event of any underwritten public offering,  enter into
and  perform  its  obligations  under an  underwriting  agreement,  in usual and
customary form including indemnity obligations, with the managing underwriter of
such  offering.  Union shall also enter into and perform its  obligations  under
such an agreement;

               (vi) Notify Union at any time when a prospectus  relating thereto
is required to be delivered  under the  Securities  Act of the  happening of any
event  as a  result  of  which  the  prospectus  included  in such  registration
statement, as then in effect, includes an untrue statement of a material fact or
omits to state a material  fact  required to be stated  therein or  necessary to
make the  statements  therein not  misleading in the light of the  circumstances
then existing;

               (vii) Cause all Common Stock registered  pursuant hereunder to be
listed  on each  securities  exchange  or  automated  quotation  system on which
similar securities issued by Tosco are then listed; and

               (viii) If the  method  of  distribution  selected  by Union is an
underwritten public offering,  and if the managing underwriter determines that a
roadshow would be beneficial to the success of the offering,  prepare a roadshow
presentation  and  make  those  executive  officers  selected  by  the  managing
underwriter  available  for meetings  with  investors  and analysts in locations
selected by the managing underwriter.

          (b) Union will make such information available to Tosco concerning the
76 Assets as is  necessary  in the opinion of counsel to Tosco to  complete  the
registration in compliance with the Securities Act.

                                       8


     8. Indemnification;  Contribution. In the event the sale or distribution of
        ------------------------------
any shares of Common  Stock by Union are  included in a  registration  statement
filed by Tosco:

          (a) Tosco agrees to indemnify and hold harmless Union,  its directors,
officers  and each  person,  if any,  who  controls  Union within the meaning of
either  Section 15 of the  Securities Act or Section 20 of the Exchange Act from
and against  any and all losses,  claims,  damages and  liabilities  (including,
without limitation,  any legal or other expenses reasonably incurred by Union or
any such controlling  person in connection with defending or  investigating  any
such action or claim) caused by any untrue statement or alleged untrue statement
of a material  fact  contained in the  registration  statement or any  amendment
thereof,  any  preliminary  prospectus  or the final  prospectus  (as amended or
supplemented  if Tosco  shall  have  furnished  any  amendments  or  supplements
thereto),  or caused by any  omission  or alleged  omission  to state  therein a
material fact required to be stated  therein or necessary to make the statements
therein  not  misleading,  except  insofar as such  losses,  claims,  damages or
liabilities  are caused by any such  untrue  statement  or  omission  or alleged
untrue statement or omission based upon information  relating to Union furnished
to Tosco in writing by Union expressly for use therein.

          (b) Union agrees to indemnify and hold harmless Tosco,  its directors,
its officers who sign the  registration  statement and each person,  if any, who
controls  Tosco within the meaning of either Section 15 of the Securities Act or
Section 20 of the  Exchange  Act to the same extent as the  foregoing  indemnity
from Tosco to Union,  but only with reference to  information  relating to Union
furnished  to Tosco in writing by Union  expressly  for use in the  registration
statement  (including any preliminary  prospectus,  the final  prospectus or any
amendments or supplements thereto).

          (c) In case any proceeding (including any governmental  investigation)
shall be instituted  involving  any person in respect of which  indemnity may be
sought  pursuant to either  paragraph  (a) or (b) of this Section 8, such person
(the  "indemnified  party") shall  promptly  notify the person against whom such
indemnity  may  be  sought  (the  "indemnifying   party")  in  writing  and  the
indemnifying  party, upon request of the indemnified party, shall retain counsel
reasonably  satisfactory to the  indemnified  party to represent the indemnified
party and any others the indemnifying party may designate in such proceeding and
shall pay the fees and disbursements of such counsel related to such proceeding.
In any such proceeding, any indemnified party shall have the right to retain its
own counsel,  but the fees and expenses of such counsel  shall be at the expense
of such indemnified party unless (i) the indemnifying  party and the indemnified
party shall have  mutually  agreed to the  retention of such counsel or (ii) the
named parties to any such proceeding  (including any impleaded  parties) include
both the indemnifying party and the indemnified party and representation of both
parties by the same counsel  would be  inappropriate  due to actual or potential
differing  interests between them. It is understood that the indemnifying  party
shall  not,  in  respect  of the  legal  expenses  of any  indemnified  party in
connection with any proceeding or related  proceedings in the same jurisdiction,
be liable for the fees and expenses of more than one separate  firm (in addition
to any local  counsel) for all such  indemnified  parties and that all such fees

                                       9


and  expenses  shall be  reimbursed  as they are  incurred.  Such firm  shall be
designated in writing by Union, in the case of parties  indemnified  pursuant to
paragraph (a) above, and by Tosco in the case of parties indemnified pursuant to
paragraph  (b)  above.  The  indemnifying  party  shall  not be  liable  for any
settlement  of any  proceeding  effected  without  its written  consent,  but if
settled with such consent or if there is a final judgment for the plaintiff, the
indemnifying  party agrees to indemnify the  indemnified  party from and against
any loss or liability by reason of such settlement or judgment.  Notwithstanding
the foregoing sentence, if at any time an indemnified party shall have requested
an indemnifying  party to reimburse the indemnified  party for fees and expenses
of counsel as  contemplated by the second and third sentences of this paragraph,
the indemnifying  party agrees that it shall be liable for any settlement of any
proceeding  effected  without  its  written  consent if (i) such  settlement  is
entered into more than 30 days after receipt by such  indemnifying  party of the
aforesaid request and (ii) such indemnifying party shall not have reimbursed the
indemnified  party in  accordance  with such  request  prior to the date of such
settlement.  No indemnifying  party shall,  without the prior written consent of
the  indemnified  party,  effect any  settlement  of any  pending or  threatened
proceeding  in  respect of which any  indemnified  party is or could have been a
party and indemnity could have been sought hereunder by such indemnified  party,
unless such settlement  includes an  unconditional  release of such  indemnified
party  from  all  liability  on  claims  that  are the  subject  matter  of such
proceeding.

          (d) To the extent the indemnification provided for in paragraph (a) or
(b) of this Section 8 is unavailable to an indemnified  party or insufficient in
respect of any losses,  claims, damages or liabilities referred to therein, then
each  indemnifying  party under such  paragraph,  in lieu of  indemnifying  such
indemnified party thereunder,  shall contribute to the amount paid or payable by
such  indemnified  party  as  a  result  of  such  losses,  claims,  damages  or
liabilities  in such  proportion as is appropriate to reflect the relative fault
of Tosco on the one hand and of Union on the other hand in  connection  with the
statements  or  omissions  that  resulted  in such  losses,  claims,  damages or
liabilities,  as  well  as any  other  relevant  equitable  considerations.  The
relative  fault of Tosco on the one hand and  Union on the other  hand  shall be
determined by reference  to, among other  things,  whether the untrue or alleged
untrue statement of a material fact or the omission or alleged omission to state
a material  fact  relates to  information  supplied by Tosco or by Union and the
parties'  relative intent,  knowledge,  access to information and opportunity to
correct or prevent such statement or omission.

          (e) The  obligations  of Tosco  and Union  under  this  Section  shall
survive  the  completion  of any  offering  of  Common  Stock in a  registration
statement under this Section, and otherwise.


     9.  Underwriting  Expenses.  Union  shall  bear  and pay  all  third-party,
         ----------------------
out-of-pocket  costs  of the  underwriting  incurred  by  Tosco in the case of a
registration  statement  filed  pursuant  to Section  6(a),  if those  costs are
incurred in the same manner as Tosco would incur in an underwritten  transaction
on  its  own  behalf.  Tosco  shall  be  responsible  for  the  expenses  of the

                                       10


underwriting  in the case of a registration  statement filed pursuant to Section
6(b) other than those additional  expenses (such as the additional  registration
fee) that are incurred as a result of the inclusion of Common Stock.  In advance
of filing a  registration  statement  pursuant to Section 6(a),  however,  Tosco
shall  present a good faith  estimate  to Union and shall  meet and confer  with
Union  regarding  the  expenses  to be  incurred.  In all cases,  Union shall be
responsible  for the  underwriting  discount and  commission on the Common Stock
sold by Union.

     10.  Termination.
          -----------

          (a) The  Agreement  shall  terminate  and be of no  further  force and
effect as to each particular  share of Common Stock, and the legend specified in
Section  3(c)(ii) shall be removed from any  certificate  evidencing such share,
immediately upon the earliest to occur of the following events:  (i) the sale or
transfer by Union of such Common Stock to any Person or Persons, other than to a
Person that is an Affiliate of Union or (ii) January 15, 2007;

          (b) The  Agreement  shall  terminate  and be of no  further  force and
effect  as to Union  immediately  upon the  earliest  to occur of the  following
events:  (i) the sale or transfer by Union of that amount of Common  Stock which
causes  Union to own less than 5% of the  outstanding  shares of Common Stock or
(ii) January 15, 2007;

          (c)  Upon  Termination  of this  Agreement  as to  Union  or as to any
particular  share of Common Stock,  the legends  defined in Section 3(c) of this
Agreement shall be removed from those shares which are no longer subject to this
Agreement;

          (d)  Notwithstanding the provisions of Section 10(a) or (b) above, the
registration  rights granted in Section 6 of this Agreement shall terminate when
all of the Common Stock could be sold under Rule 144 (or successor rule) without
any volume limitations.

     11.  Agreement to Perform  Necessary Acts. Union and Tosco shall do any and
          ------------------------------------
all things,  take any and all actions,  perform any further acts and execute and
deliver any further  documents that may be reasonably  necessary,  whether under
any applicable law, the Articles and Bylaws of Tosco or otherwise,  to carry out
and effectuate the provisions of this Agreement;

     12.  Governing Law. This Agreement shall be governed by and construed under
          -------------
the laws of the State of New York.

     13.  Integration.  This  Agreement  constitutes  the entire  agreement  and
          -----------
understanding  of Tosco and Union  with  respect to the  subject  matter of this
Agreement and supersedes all prior  agreements and  understandings  with respect
thereto.

                                       11



     14.   Counterparts.   This  Agreement  may  be  executed  in  two  or  more
           ------------
counterparts,  each of  which  shall be  deemed  an  original,  but all of which
together shall constitute one and the same instrument.

     15. Titles and  Subtitles.  The titles and subtitles used in this Agreement
         ---------------------
are used for  convenience  only and are not to be  considered  in  construing or
interpreting this Agreement.

     16.  Notices.  Unless  otherwise  provided  herein,  any notice required or
          -------
permitted  under this  Agreement  shall be given in writing or by facsimile  and
shall,  subject to the provisos set forth below, be deemed effectively given (i)
upon personal  delivery to the party to be notified at the address indicated for
such party on the signature page hereof,  (ii) on the next Business Day after it
is deposited with a recognized overnight courier service servicing the locale of
the addressee,  designated for overnight delivery,  prepaid and addressed to the
party to be notified at the address  indicated  for such party on the  signature
page hereof,  or (iii) upon  transmission to such party at its facsimile  number
indicated  for  such  party  on  the  signature  page  hereof  (with  electronic
acknowledgment  of  receipt  and a copy  thereof  sent by  overnight  courier in
accordance  with clause (ii)  above);  provided,  however,  that any such notice
shall be sent to such  other  address  or  facsimile  number  as such  party may
designate by ten (10) days' advance notice to the other party.

     17. Enforcement Expenses. If any action at law or in equity is necessary to
         --------------------
enforce or interpret the terms of this Agreement,  the prevailing party shall be
entitled to reasonable  attorneys'  fees,  costs and necessary  disbursements in
addition to any other relief to which such party may be entitled.

     18. Amendments and Waivers. Except as expressly provided in this Agreement,
         ----------------------
neither this Agreement nor any term hereof may be amended, waived, discharged or
terminated  other than upon the written consent of all of (i) Tosco and (ii) the
holders of at least a majority  of the Common  Stock.  Any  amendment  or waiver
effected in accordance  with this paragraph shall be binding upon each holder of
Common Stock and Tosco. In the event that an  underwriting  agreement is entered
into  between  Tosco  and any  holder  of Common  Stock,  and such  underwriting
agreement  contains  terms  differing from this Agreement as to any such holder,
the terms of such underwriting agreement shall govern.

     19. No  Reliance  on Other  Parties.  Each  party  hereto  has  voluntarily
         -------------------------------
undertaken its  obligations to the other parties hereto under this Agreement and
each of the other  contracts  and  instruments  referred  to herein.  Each party
hereto represents and warrants that it has reviewed and understands each of this
Agreement and such other documents and has discussed each such document with its
legal counsel (and other advisors,  if any) so that such party is satisfied that
it is aware of its risks and the significance of each such document.  Each party
acknowledges  and  agrees  that  it is  not  relying  upon  any  representation,
warranty,  understanding  or  obligation  of any other party  hereto that is not
expressly stated in this Agreement or any other contract or instrument  referred
to herein.

                                       12



     20.  Severability.  If one or more provisions of this Agreement are held to
          ------------
be  unenforceable  under  applicable  law, such provision shall be excluded from
this Agreement and the balance of the Agreement  shall be interpreted as if such
provision  were so excluded  and shall be  enforceable  in  accordance  with its
terms.

     21.  Business  Days.  If any date set forth  herein as the final  date (for
          --------------
purposes of payment, notice or otherwise) is not a Business Day, then such final
date  shall be deemed to be the next  succeeding  Business  Day.  Time is of the
essence under this Agreement.







          IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first above written.


                             TOSCO CORPORATION
                             a Nevada corporation


                             By
                                  ---------------------------------
                                  Name:
                                  Title:

                             Address for Notices:

                             Tosco Corporation
                             72 Cummings Point Road
                             Stamford, Connecticut 06902

                             Attn:  Wilkes McClave III, Esq.
                                    General Counsel
                                    (203) 977-1005 (Phone)
                                    (203) 964-3187 (Fax)

                             UNION OIL COMPANY OF CALIFORNIA
                             a California corporation


                             By
                                  --------------------------------
                                  Name:
                                  Title:

                             Address for Notices:

                             UNOCAL Corporation
                             2141 Rosecrans Avenue, Suite 4000
                             El Segundo, California 90245

                             Attn:  Neal E. Schmale
                                    Chief Financial Officer
                                    (310) 726-7621 (Phone)
                                    (310) 726-7806 (Fax)

                             cc:    Dennis P.R. Codon, Esq.
                                    General Counsel
                                    (310) 726-7651 (Phone)
                                    (310) 726-7815 (Fax)




                         SUPPLEMENT NO. 1 TO

              STOCK PURCHASE AND SHAREHOLDER AGREEMENT


          Tosco  Corporation  hereby  elects  that the $45 per share  limitation
contained in the  definition  of Market Price set forth in Section 1, on page 2,
of the Stock Purchase and Shareholder Agreement dated January 15, 1997 shall not
apply.

          IN WITNESS WHEREOF, Tosco Corporation has executed this as of the 15th
day of January, 1997.


                             TOSCO CORPORATION
                             a Nevada corporation


                             By
                                 ---------------------------------
                                 Name:
                                 Title: