A fuel tax (also known as a petrol tax, gasoline tax, gas tax or fuel duty) is a sales tax imposed on the sale of fuel. In the United States, the funds are often dedicated to transportation, or roads, so that the fuel tax is considered by many a user fee. In other countries, the fuel tax is a source of general revenue, which pays for many projects. So let us see if the price of fuel is really different when you subtract tax?
UK
From 2007-10-01 the main road fuel (petrol and diesel) duty rate in the UK is GBP£0.5035 per liter. The rate for biodiesel and bioethanol is £0.3035. Value Added Tax (VAT), currently at 17.5%, is also charged on the price of the fuel and on the duty. At a pump price of 128.8p/liter (typical for diesel as of May 2008), this would put the combined tax at 69.53p/liter, or approximately USD$5.16 per US gallon.
US
Fuel taxes in the United States varies by state. For the first quarter of 2008, the average state gasoline tax is 28.6 cents per gallon, plus 18.4 cents per gallon federal tax making the total 47 cents per gallon (12.4 cents/L). For diesel, the average state tax is 29.2 cents per gallon plus an additional 24.4 cents per gallon federal tax making the total 53.6 cents per gallon (14.2 cents/L).
Take the average price per gallon in UK 8.47 as of 5/26 and US 4.16 subtract tax
US = 3.69/gal
UK = 3.31/gal
Actually there is not that much different now is it, and the price is actually cheaper by 38c in UK