Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statements Nos. 333-227095, 333-154708, and 333-188451 on Form S-8 of our report dated June 21, 2019, appearing in this Annual Report on Form 11-K of the Texas Oil and Chemical Co. II, Inc. 401k Plan, for the year ended December 31, 2018.

/s/ BKM Sowan Horan, LLP

Addison, Texas

June 21, 2019