Some states do add sales taxes to fuel costs, however, most states tax the fuel at a per-gallon rate. The fed rate on fuel has been 18.4 cents/gallon for gas and 24.4 cents/gallon for diesel for years now. So, in actuality, the higher the price of fuel, the lower the effective tax rate (again, the exception being where sales taxes are tacked on to the price).
Los Angeles county is bad. Even with the car culture we have here, people are starting to take substitutes like public transportation. Some people are starting to fuel in nearby Orange county where the taxes are lower.