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.rom what I found the density of olive oil, which probably is a  similar density to vegetable oil, is about 7.64 lb/gallon. So 1  gallon of vegetable oil will weigh approxim … ately 7.6 lbs. Crude  corn oil (Vegetable oil) weighs 7.7 lbs per gallon.