Tex. Natural Resources Code § 115.018

(a) A person authorized to transport oil or a petroleum product on a manifest issued by a shipper may not receive:

(1) a commodity for transportation that is different from the commodity described in the manifest; or

(2) oil or a petroleum product in an amount exceeding the amount authorized by the manifest.

(b) A person authorized to transport oil or a petroleum product by a shipper-issued manifest that bears on its face the date and serial number of the tender may rely on the manifest delivered to that person and each consignee or person to whom the transporter delivers oil or a petroleum product covered by that manifest may rely on the manifest as authority to receive the commodity delivered if the manifest:

(1) appears to be valid on its face;

(2) is signed by the shipper; and

(3) bears the certificate of the shipper that the transportation of the oil or petroleum product is authorized by the tender.

(c) If the commission by order prohibits the transportation of oil or a petroleum product by motor vehicle without a manifest that shows the date and serial number of a tender authorizing the transportation, a person may not ship or transport or cause to be shipped or transported by motor vehicle oil or a petroleum product unless the person furnishes the manifest to the operator of the motor vehicle. The person transporting the oil or petroleum product shall maintain the manifest in the vehicle at all times during the shipment. If the person to whom the tender is issued is the operator of the motor vehicle and the tender identifies the motor vehicle by license number and covers one load, the person may carry the tender in the vehicle in lieu of a manifest.