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You may call it off-road diesel, or red-dyed diesel, or untaxed diesel. But whatever its name, itā€™s the same affordable fuel. You can find off-road diesel at many large gas stations. Chemically it is identical to on-road diesel, but it is much cheaper. Unfortunately, it is seriously illegal to fill your truckā€™s gas tank with off-road diesel.

Why canā€™t you run off-road diesel in a truck?

On-road diesel prices include a substantial federal and state highway tax. Off-road diesel fuel has not been taxed for on-road use. Therefore, burning this dyed diesel while on the road is tax evasionā€“a serious crime.

The silhouette of an illuminated gas station canopy at night with off road diesel for sale.
Gas station | Maarten van den Heuvel via Unsplash

According to LearnDiesels.com, the reason you canā€™t run off-road diesel in your truck comes down to money. Taxes to be exact. The federal government adds a 24.4 cent highway tax to every gallon of diesel fuel. State taxes range from 12 cents to 67 cents.

Itā€™s hardly fair for farmers and construction workers who run diesel engine equipment off-road to pay a highway tax for every gallon of fuel. Therefore, the government allows untaxed off-road diesel for non-highway use. But all of this untaxed diesel must be dyed bright red so police officers and other government officials can easily identify it in a truckā€™s gas tank.

Can you run off-road diesel in a vehicle?

Once upon a time, off-road diesel had a higher sulfur content. Today, off-road diesel is identical to regular on-road diesel. From a mechanical point of view, you can run off-road diesel in any vehicle that takes on-road diesel.

Detail shot of the Cummins Turbo Diesel badge on the fender of a gray Ram 3500 pickup truck.
2022 Ram Cummins turbo diesel badge | Stellantis

Whatā€™s the deal with sulfur? Diesel fuel with a high percentage of sulfur creates especially nasty emissions gases. But diesel with low sulfur is further refined, burns less efficiently, and does a worse job lubricating your engine.

When the Environmental Protection Agency (EPA) required ultra-low sulfur diesel (ULSD) fuel, engine manufacturers had to adapt. Because many off-road engines (agricultural, construction, or generators) have a longer lifespan than on-road engines, the EPA gave off-road diesel sellers a longer timeline to switch to ULSD. But as of 2014, all off road diesel is chemically identical to on-road diesel.

What happens if you get caught using off-road diesel?

Most states levy a minimum $1,000 fine (per gas tank) against motorists using off-road diesel on the road. These states will charge $10/gallon if that comes out to a larger fine. Some states charge more. One Georgia driver allegedly faced $50,000 in finesā€“according to PowerStroke.org.

Publicity shot of a heavy duty Ram diesel parked in a lot overlooking a city.
2022 Ram 3500 | Stellantis

It is seriously illegal to fill your diesel truck up with off-road diesel. It is actually illegal on several levels: this crime is a tax evasion that breaks both state and federal laws. Therefore, multiple agencies could come after you for off-road diesel misuse.

In addition, it is very easy to get caught with off-road diesel. Manufacturers must dye this nontaxed diesel so heavily, that a single gallon in a gas tank will be enough for a police officer or other official to detect.

With soaring gas prices, filling your tank with off-road diesel is more tempting than ever. But because everyone is tempted, enforcement officials may well be checking tanks more often.

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