Oil does not come from dead dinosaurs. The fossil fuels, the name given as such, originates from commitment of oil producers to make it appear as scarce.
"Most oil reserves were formed between 65 and 252 million years ago. While this does overlap with the ‘dinosaur times’, oil is a marine sediment made of the remains of algae and plankton.

Skeletons of prehistoric reptiles such as plesiosaurs and ichthyosaurs (neither of which count as dinosaurs) have been found in the same geological layers as oil and they may have contaminated the oil deposit. But to say that oil is made from dinosaurs is like saying that bread is made from insects, just because the odd one occasionally falls into a flour mill." - www.sciencefocus.com/planet-earth/dinosaurs-in-fossil-fuel

Important to note, many "depleted" oil wells replenish themselves over time.