I think what you will find is that diesel fuel in general is taxed at a slightly higher rate than gasoline. However, I don't know of any states that tax the diesel fuel going into a car or light truck at a different rate then the diesel fuel going into a "heavy" truck . There may be some states that do that, but it's probably limited to a 3 or 4 at most - but I don't know for sure. Diesel fuel used in "off-road" trucks (farms, mines, construction equipment, etc.) doesn't have to pay some of those taxes. But that is a completely different topic.
