What is the carbon content, by weight, of vegetable oil?
Vegetable oils are mainly made of glycerol esters of oleic acid, linoleic acid and palmitic acid. For example, the fatty acids extracted from olive oil are a mixture of $74$% oleic acid, $11$% palmitic acid, and $10$% linoleum acid, plus 5% other acids. These proportions are average values that may change from one sample to the next one.
The mass proportion of carbon atom is $77.2$ % in glycerol trioleate, $78.3$ % in glycerol trilinoleate, and $75.8$ % in glycerol tripalmitate