What is Red Diesel Fuel?

So, the reason red fuel exists is actually really simple: taxes. All fuels are taxed as part of a “fuel tax,” and that tax occurs at the point of sale. Most countries in the world enforce a fuel tax of some kind because, you know, there are not already taxes enough crushing down on citizens as governments get more power-hungry and careless with their spending.


State and local taxes are factored into the price you pay for clear diesel at the pump, which is supposed to be allocated to the building, repair, and maintenance of your state’s roadways. Income tax, property tax, vehicle tax, registration based on vehicle, and all those other insane aren’t enough, apparently. It’s almost like the government has no incentive to run efficiently since they’re funded by stolen money from citizens. Anyways.

With that in mind, red diesel exists for non-road use, in the sense that red diesel is specifically created for agricultural use, railways, boats, trains, planes, generators, tractors, heaters, refrigerators, and other “off-road” applications. Basically, if you have a diesel engine in a vehicle of some sort that won’t be used on the road, you can use red diesel, and since it’s taxed much differently, it’s much cheaper than standard diesel.

Right off the bat here, I want to say that red diesel is chemically identical to the standard diesel fuel you’ll find at any gas station, which is just ultra-low sulfur diesel. The only difference you’ll find between normal diesel and red diesel is the oil-soluble red dye they put in it.

Why is it Dyed?

You might be wondering, why do they bother dying it? And they do this to check who’s using this fuel and who isn’t. You have to remember, if it’s being taxed less, it costs you less, and there’s no barrier to entry to get this cheaper fuel. Of course, it’s not at all gas stations. In fact, it can be hard to find depending on where you live, but you’ll typically find it in very rural areas or very small towns where there is a farming or industrial type of work going on, where their equipment can use this fuel.

Back to what I was saying, the reason it’s dyed red is so they can catch people using it illegally. Because there’s no barrier to entry and you can pump it yourself at gas stations that have it, there’s obviously an incentive to cheat the system and get the cheaper fuel to save yourself money. The problem is, when your tank gets dipped, which is when it’s checked by some sort of government works, if they find red diesel and you’re on the road, you can face some pretty big ass fines.

Funny enough, red diesel actually can be used on the road in the form of road construction equipment, just not in vehicles used on the road.

Penalties and Fines

The penalties for running red diesel in a road application vary from country to country, and it varies by the state level in the U.S. as well. For reference, where I am right now in Arizona, the fine for illegal using red diesel is a minimum of $1000 or $10 per gallon, depending on which is more. Multiple offenses can quickly result in even heavier fines or criminal charges.

Typically when checking for illegal red diesel, they’ll start at your fuel tank and take a small sample of it to check the color. This can literally just be as simple as putting a straw in your tank, covering the top of it, and then pulling it back out. Sometimes they’ll even spin the fuel filter and observe for obviously dyed fuel.

Sometimes though, they’ll take it even further and use a special black light that will glow an obvious color denoting dyed fuel was previously used on that vehicle. They’ll put the light on the filter, fuel tanks, and other areas they can easily access. If they see signs that red diesel was used, they can give you a ticket or a court date right then and there.

The red dye itself is a synthetic azo dye called Solvent Red 26, and it’s the standard dye mandated by the U.S. IRS to distinguish between off-road fuel and clear road fuel. Solvent Red 26 is also mandated by the EPA for use in high sulfur diesel fuel. That’s where things get confusing and where some people think the articles they’re seeing of people putting red fuel in their trucks is going to ruin their trucks.

High Sulfur vs Low Sulfur Fuel

Modern fuel systems aren’t designed for high sulfur diesel fuel, and high sulfur duel is dyed the same color as off-road diesel fuel. But it’s not something you really need to worry about because nearly all about 99% of red-dyed diesel fuel in the U.S. is chemically identical to the standard ultra-low sulfur fuel you’d get at the pump.

The U.S. switched the standard to ultra-low sulfur diesel fuel in 2006, so trucks and equipment produced after 2006 are almost all designed to run on this low sulfur fuel. On the other hand, engines produced prior to 2006 were designed to use low sulfur fuel, with the difference between low sulfur and high sulfur fuel being a pretty big difference. For reference, ultra-low-sulfur content is limited to 15 ppm, while low-sulfur is limited to 500 ppm and high sulfur diesel contains more than 500 ppm.

The switch from low-sulfur fuel to ultra-low-sulfur fuels makes a big difference in lubricity, with most of it being stripped away. However, this can be band-aided with a quality fuel additive.

How to Get Red Diesel?

No special license is required to sell red diesel, but the seller has to be certified to carry it, which means they’re probably supposed to tell somebody if they see you pumping red fuel in your truck and then driving down the road. You can also get this fuel directly delivered to your farm, jobsite, or whatever you’re doing that requires that fuel. It’ll come directly from a wholesale fuel distributor who will deliver it to you, and sometimes they even offer services for renting their fuel tanks just in case you don’t have a big fuel tank at your location.

In some countries, their dyed fuel isn’t red. There are countries out there with blue diesel, green diesel, and more. But, they dye their diesel fuel for the exact same reasons: which is to check who is using it and who isn’t. We even have blue-dyed diesel here in the U.S., but that’s reserved for federal government fleets, so you definitely don’t want to get caught with blue diesel in your truck unless you feel like going to prison for stealing from the federal government.

Jet A and Jet A-1 fuel used in aircraft is close in chemical makeup to diesel fuel and is often dyed blue, green, red, and even purple.

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