Weight of Oil One gallon of oil is 6-8 pounds depending on density. If you assume SAE 10W-30 oil; density is 875 grasm/litre = 1.929 pounds per litre = 7.3 pounds per US gallon. Assume SAE 10W-30 oil; density is 875 grasm/litre = 1.929 pounds per litre = 7.3 pounds per US gallon. Cheers Malcolm.