The gasoline that you put in your petrol motor is C5H12 to C7H16, a mixture of the isomeric pentanes and hexanes, and a few heptanes. The gas that you put in your diesel motor has one degree of unsaturation, i.e. C6H12 to C10H20; with the possibility of geometric isomerism, diesel is a bit of a witches' brew.
Most of the time, when we want to represent gasoline, we would use the formula C6H14, i.e. hexanes; and of course hexanes could be a mixture of isomers: dimethylbutanes; ethylbutane methylpentanes; and n-hexane.
In the laboratory, often we use so called petroleum ethers, with various boiling point ranges, 40−60 ∘C, 60−80 ∘C, 100−120 ∘C. These tend to contain some unsaturated material.
