Farmers tend to have more than one grade of fuel. dyed diesel is the most common grade because there is no road tax. Farmers that aren't close to town (most of them) are likely to have undyed diesel for their trucks as well. Gasoline is somewhat common - though gasoline tractors went out of style around 1960, sometimes there is a car that never goes to town, lawnmowers, ATVs... It depends on the farm what they keep on hand.