The answer is easy. The U.S. government passed a law (Moss/Magnuson) requiring auto makers to meet a minimum fuel economy rating for the entire fleet of vehicles they produce. If the auto maker fails to meet this requirement, they are charged a *gas guzzler* tax.

The bigger the company, the easier it is for them to meet the requirement and to cheat a bit. For example, Ford produces lots of gas guzzling vehicles but Ford can balance that by producing enough small cars to balance out the big stuff.

Fuel economy is simply the calculated EPA ratings. Now if a company produces millions of vehicles any small improvement in their EPA ratings helps a lot. Hence, big American and Japanese companies recommend very low viscosity oils so they can claim an improvement of one or two tenths better *calculated* economy. Multiply that by millions of vehicles and it helps them balance their gas guzzler problems. They tell the public that these are *economy* oils recommended to improve economy when in fact they have almost no impact in the real world and would never be recommended if it wasn't for Moss/Magnuson.

European auto makers are now the only ones who put reliability ahead of their fuel economy problems.

BTW, a Mercedes V12 owner getting better mileage has to pay a gas guzzler tax while Ford Expedition owners do not.

Of course Detroit gets a big break from the politicians. Half of their production are trucks and SUV's. These vehicles have a lower fuel economy standard than cars.

Finally, the fact that both Honda and Ford recommend 5W-20 viscosity's indicate where their priorities lie.