1 EXHIBIT 23.3 CONSENT OF INDEPENDENT PETROLEUM ENGINEERS AND GEOLOGISTS We hereby consent to the reference of our firm in the Annual Report on Form 10-K of Tesoro Petroleum Corporation for the year ended December 31, 1997, and the incorporation by reference of such report into the Registration Statement on Form S-3 (No. 333-51789) of our reserve report dated as of December 31, 1997. We also consent to the references to us, including the reference under the heading "Experts" in the Prospectus Supplements, which are a part of such Registration Statement on Form S-3. NETHERLAND, SEWELL & ASSOCIATES, INC. By: /s/ FREDERIC D. SEWELL --------------------------------- Frederic D. Sewell President Dallas, Texas June 5, 1998