You have to do some simple math to understand why oil use does not go down as much as you think it will when prices go up. About 28% of all oil use is non-fuel in nature. Demand in that 28% of the market doesn’t go down appreciably when the price of oil goes up.
So, using less gasoline only affects 72% of the market for oil. Also, there is a lot of fuel use that is inelastic. A certain amount of driving happens at all price levels. Local, state and federal government vehicles for example drive just at much as high prices as at low ones. Business related driving adjusts much less than the price of gasoline would suggest also.
Decrease is gasoline use starts with low income people and slowly leaks upward. As you reach higher income levels, people drive about the same miles no matter what the price (so far).
This is why gasoline use is defined as inelastic.
That sounds too high. Do you have a source for that information?
Petroleum Product Supplied http://eia.doe.gov/dnav/pet/pet_cons_psup_dc_nus_mbblpd_m.htm