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                                                                     EXHIBIT 5.1



                   [Letterhead of Vinson & Elkins L.L.P.]





                                   April 9, 1998

Quaker State Corporation
225 East John Carpenter Freeway
Irving, Texas  75062

                 Re:      Quaker State Corporation
                          Registration Statement on Form S-3 (No. 333-33133)
                          Debt Securities
                          Capital Stock, par value $1.00 per share
                          Warrants

Ladies and Gentlemen:

         We have acted as counsel for Quaker State Corporation, a Delaware
corporation (the "Company"), in connection with the registration under the
Securities Act of 1933 (the "Securities Act") on a Registration Statement on
Form S-3 (No. 333-33133) (the "Registration Statement") of the offer and sale
from time to time pursuant to Rule 415 under the Securities Act of the
following securities for an aggregate initial offering price not to exceed
$400,000,000:  (i) debt securities of the Company (the "Debt Securities"); (ii)
shares of capital stock, par value $1.00 per share, of the Company (the
"Capital Stock"); and (iii) warrants to purchase Debt Securities or Capital
Stock (the "Warrants" and, together with the Debt Securities and Capital
Stock, the "Offered Securities").

         For purposes of rendering the opinions contained in this letter, we
have reviewed those agreements, records, documents, and matters of law as we
have deemed relevant in order to render the opinions set forth herein, including
but not limited to (a) the Composite Certificate of Incorporation and the Bylaws
of the Company, (b) resolutions adopted by the Board of Directors of the
Company, and (c) the form of Indenture filed as Exhibit 4.3 to the Registration
Statement to be executed by the Company and the trustee (the "Indenture"),
pursuant to which Debt Securities may be issued.

         As to certain questions of fact material to our opinions, we have
relied upon certificates from officers of the Company and other persons, as
appropriate, and upon certificates of public officials.
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Quaker State Corporation
April 9, 1998
Page 2


         Based upon and subject to the foregoing and subject further to the
assumptions, exceptions and qualifications hereinafter stated, we express the
following opinions:

         1.       With respect to shares of Capital Stock, when both (A) the
Board of Directors of the Company or, to the extent permitted by Section 141(c)
of the General Corporation Law of the State of Delaware, a duly constituted and
acting committee thereof (such Board of Directors or committee being
hereinafter referred to as the "Board") has taken all necessary corporate
action to approve the issuance of and the terms of the offering of the shares
of Capital Stock and related matters and (B) certificates representing the
shares of Capital Stock have been duly executed, countersigned, registered and
delivered either (i) in accordance with the applicable definitive purchase,
underwriting or similar agreement approved by the Board upon payment of the
consideration therefor (not less than the par value of the Capital Stock)
provided for therein or (ii) upon conversion or exercise of any other Offered
Security, in accordance with the terms of such Offered Security or the
instrument governing such Offered Security providing for such conversion or
exercise as approved by the Board, for the consideration approved by the Board
(not less than the par value of the Capital Stock), then the shares of Capital
Stock will be legally issued, fully paid and nonassessable.

         2.       With respect to Debt Securities to be issued under the
Indenture, when (A) the Indenture has been duly authorized and validly executed
and delivered to the trustee by the Company, (B) the Indenture has been duly
qualified under the Trust Indenture Act of 1939, (C) the Board has taken all
necessary corporate action to approve the issuance and terms of such Debt
Securities, the terms of the offering thereof and related matters, and (D) such
Debt Securities have been duly executed, authenticated, issued and delivered in
accordance with the provisions of the Indenture and the applicable definitive
purchase, underwriting or similar agreement approved by the Board upon payment
of the consideration therefor provided for therein, such Debt Securities will be
legally issued and will constitute valid and binding obligations of the Company,
enforceable against the Company in accordance with their terms, except as such
enforcement is subject to  any applicable bankruptcy, insolvency, reorganization
or other law relating to or affecting creditors' rights generally and general
principles of equity (regardless of whether such enforceability is considered in
a proceeding in equity or at law).
         
         3.       With respect to the Warrants, when (A) the Board has taken
all necessary corporate action to approve the creation of and the issuance and
terms of the Warrants, the terms of the offering thereof, and related matters,
(B) the warrant agreement or agreements relating to the Warrants have been duly
authorized and validly executed and delivered by the Company and the warrant
agent appointed by the Company, and (C) the Warrants or certificates
representing the Warrants have been duly executed, countersigned, registered
and delivered in accordance with the appropriate warrant agreement or
agreements and the applicable definitive purchase, underwriting or similar
agreement approved by the Board upon payment of the consideration therefor
provided for therein, the Warrants will be legally issued.
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Quaker State Corporation
April 9, 1998
Page 3


         The opinions expressed above are subject in all respects to the
following assumptions, exceptions and qualifications:

         a.       We have assumed (i) all information contained in all
documents reviewed by us is true and correct, (ii) all signatures on all
documents reviewed by us are genuine, (iii) all documents submitted to us as
originals are authentic and complete, (iv) all documents submitted to us as
certified or photostatic copies conform to authentic originals thereof, (v) each
natural person signing any document reviewed by us had the legal capacity to do
so, (vi) each person signing in a representative capacity any document reviewed
by us had authority to sign in such capacity, and (vii) the laws of any
jurisdiction other than Texas that govern any of the documents reviewed by us or
referenced in this opinion letter (other than the Company's Composite
Certificate of Incorporation and Bylaws) do not modify the terms that appear in
any such document.
         
         b.       We have assumed that (i) the Registration Statement and any
amendments thereto (including post-effective amendments) will have become
effective and comply with all applicable laws; (ii) the Registration Statement
will be effective and will comply with all  applicable laws at the time the
Offered Securities are offered or issued as contemplated by the Registration
Statement (if such offering or issuance requires the delivery of a prospectus
under the Securities Act or pursuant to any other law); (iii) a Prospectus
Supplement will have been prepared and filed with the Securities and Exchange
Commission describing the Offered Securities offered thereby and will comply
with all applicable laws; (iv) all Offered Securities will be issued and sold
in compliance with applicable federal and state securities laws and in the
manner stated in the Registration Statement and the appropriate Prospectus
Supplement; (v) a definitive purchase, underwriting or similar agreement with
respect to any Offered Securities offered or issued will have been duly
authorized and validly executed and delivered by the Company and the other
parties thereto; and (vi) any Offered Securities issuable upon conversion,
exchange or exercise of any Offered Security being offered or issued will be
duly authorized, created and, if appropriate, reserved for issuance upon such
conversion, exchange or exercise.

         c.       In rendering the opinion in paragraph 2, we have assumed that
the trustee is or, at the time the Indenture is signed, will be qualified to
act as trustee under the Indenture and that the trustee has or will have duly
executed and delivered the Indenture.
         
         d.       We express no opinion with respect to (i) the enforceability
of provisions in the Indenture or any other agreement or instrument with
respect to delay or omission of enforcement of rights or remedies, or waivers
of defenses, or waivers of benefits of stay, extension, moratorium, redemption,
statutes of limitation, or other nonwaivable benefits bestowed by operation of
law; or (ii) the enforceability of indemnification or contribution provisions
to the extent they purport to
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Quaker State Corporation
April 9,1998
Page 4

relate to liabilities resulting from or based upon negligence or any violation
of federal or state securities or blue sky laws.

         e.       We express no opinion as to the requirements of or compliance
with federal or state securities laws or regulations.
         
         f.       We note that the Indenture by its terms purports to be
governed by the laws of the State of New York and that the terms of the
Warrants, when determined, may be governed by the laws of a jurisdiction other
than the State of Texas or other than the General Corporation Law of the State
of Delaware.  While we express no opinion with respect to the laws of the State
of New York or such other jurisdictions in rendering these opinions, we have
assumed that the internal laws of the State of New York and such other
jurisdictions are the same as the internal laws of the State of Texas.  We have
not conducted any analysis to determine whether that assumption is correct.
         
         g.       The opinions expressed in this letter are limited to the laws
of the State of Texas, the General Corporation Law of the State of Delaware,
and the federal laws of the United States of America.  You should be aware that
we are not admitted to the practice of law in the State of Delaware.

         We consent to the filing of this opinion of counsel as Exhibit 5.1 to
the Registration Statement.  We also consent to the reference to this firm
under the heading "Legal Opinions" in the Prospectus forming a part of the
Registration Statement.  In giving this consent, we do not admit that this firm
is in the category of persons whose consent is required under Section 7 of the
Securities Act or the rules and regulations of the Securities and Exchange
Commission promulgated thereunder.

         We disclaim any duty to advise you regarding any changes in, or
otherwise communicate with you with respect to, the matters addressed herein.

                                    Very truly yours,
                                             
                                    /s/ Vinson & Elkins L.L.P.