A lot of it depends on how much difference you pay for the higher octane product. In the Texas Gulf Coast region there is a 10 cent spread between 87 octane and 93 octane premium at the rack. My dispensers blend the 2 to make 89 octane midgrade. In order to be classified as premium, the 93 octane must contain twice the detergent additive as 87 octane which is a big plus with EFI engines. If you take a look at these DOE figures by clicking on the regioun PADD 3 is the Texas Gulf Coast. http://tonto.eia.doe.gov/dnav/pet/pet_pri_gnd_dcus_r30_w.htm Historically our area is the cheapest in the nation. This is due to fierce competition. Federal motor fuel tax is the same all over the US. State tax varies from state to state.