I see some gas stations selling “off-road diesel”. What is the difference? If it’s not as pure, wouldn’t it gum up an off-road vehicle’s engine just as badly? What’s the deal? - Jinx
One difference is the off-road diesel (for farm machinery) does not have the road tax.
I don’t know if is formulated differently/is dirtier than on-road diesel.
Brian
The diference is taxes. Here in the US fuel sold for on-road use has a bunch of taxes built into the price.
Fuel used by construction equipment, stationary equipment, farm tractors etc does not have to pay these taxes.
As an aside every heavy equipment operator I have ever met, that had a diesel piece of machinery, also drove a diesel pickup.
Gee I wonder why? 
Damn, beaten by a slow hampster!
N9IWP fuel is the same only the price is different
Off road Diesel has red dye added to make it easier to catch the folks who cheat! As mentioned, it’s also cheaper, about $.35 a gallon in MO. Over the road trucks may have their fuel checked at weight stations or roaming check points. I’m told the fine is quite severe.
It also MAY have a higher sulpher content than that allowed for on road fuel. But in many cases it’s the same fuel with the dye added.
In Europe, road and off-road diesel fuels are dyed different colors to give inspectors a visual check to catch cheaters.
Is a similar system used in US?
The pump where I buy off-road diesel for my tractor is labled “low sulfur” so I assume it is the same as on-road except that it is dyed red.
It used to be very common for people to cheat and put off-road diesel in their pickups. I don’t know anyone who does it anymore. The fine is very large, something like $1,000 minimum, and there are constant rumors of the feds checking the tanks on trucks for red fuel.
Taxes on fuel are a complicated mess because the fuel is supposed to be taxed according to its use so you would have different taxes depending of whether the fuel is used for stationary machinery, on road vehicles, pleasure marine boating, work related marine uses, etc.
Sometimes you just have to buy different fuel which is colored differently. Sometimes you pay the tax and can claim a refund later. It is crazy but the fuel is the same.
Note that there are different grades of diesel and that it is not that one is better or worse that the others. There are just different formulations.
Some people are under the impression that diesel fuel is of lower quality than gasoline. This is not true at all. If anything, diesel has to be better filtered because injectors would not tolerate any junk.