Is It Really Illegal To Fill Your Pickup Truck With Off-Road Diesel?

You may call it off-road diesel, or red-dyed diesel, or untaxed diesel. But whatever its name, it’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 truck’s gas tank with off-road diesel.

Why can’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 evasion–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

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According to LearnDiesels.com, the reason you can’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.

It’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 truck’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

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What’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 fines–according to PowerStroke.org.

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

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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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