Diesel Fuel

What Color is Diesel Fuel?

May 24, 2022 7:59 pm Published by Leave your thoughts

One of the most common diesel colors people run into, particularly for off-road use, tends to be red-dye diesel. However, unless one works as a truck driver, mechanic, automotive industry role or similar, it would be easy to think all diesel comes in the color red. This is incorrect. Diesel as vehicle fuel is available in a number of different colorations, all of which are intended to signal different uses.

What Color is Diesel Fuel?

For the most part, regular diesel without any additives for any reason is either clear-colored or amber, depending on the extent of filtering. For the most part, the majority of folks never know this as they typically just take the end of the diesel hose on a pump, insert it into the tank opening and turn on the lever. However, off-road enthusiasts and truck drivers typically have to manage an open flow or a flow into a portable container, and the coloring of the diesel used becomes far more obvious in those instances. 

The above said, filtering has a huge impact. Really bad diesel, i.e., refined very poorly, tends to be far browner in coloring as it contains more contaminants in it. This is a poor fuel to run an engine on as those contaminants will eventually contribute to gunk and problems as the diesel burns in the engine combustion process. The extremely clean version, in comparison, has been filtered and sanitized to reduce its resulting pollution. It runs cleaner than poor grade diesel and can be hard to distinguish from gasoline due to its clarity. 

The Source of Natural Coloring

Diesel is an end product from burning and refining petroleum (crude oil). The sulfur content has a significant impact on the coloring. At the bottom end of the spectrum, a significant amount of sulfur is present, darkening the diesel considerably. Many of these products still have their use, oftentimes used in heavy machinery and tractors that don’t need to be fussed with in terms of super-refined diesel. The standard, lower grade burns efficiently still, even better than gasoline with less output, despite all the stereotypes of diesel engines belching clouds of exhaust smoke. 

Added Coloring

Depending on how diesel is used, however, additives can be included to signal the use of the fuel as well as its taxation. The added color is used to identify the fuel for different uses, ranging from boats to trucks and heavy equipment to off-road vehicle use. 

Intentionally colored diesel typically tends to be in either red or blue variations. This is a quick, immediately recognizable status to help identify that the fuel type should not be taxed. Normally, people pay taxes on all vehicle fuel they purchase at the pump. Colored diesel, however, has no such taxes because the vehicle is not supposed to be used on public roads. While this saves money, it also restricts the fuel to the usage intended. So, for example, someone caught fueling a truck with red-dyed diesel that is used on the highway could face a hefty penalty. Most pump operators are expected to be on the watch for this sort of behavior as well. 

Red diesel is most often used for agrarian vehicles such as tractors, water trucks, pumps and similar. It’s a poor grade fuel, and if used in a road vehicle, that engine is going to start bucking and having issues after a while. Farming equipment can also be designated to use green-dyed diesel as well. The coloring scheme depends on the state laws for a given region. This can be a bit confusing for new folks going back and forth across borders for better pricing, but most farmers and supporters figure it out pretty quickly for the local area they are working in. 

In the boating world, colored diesel is an immediate signal there’s a problem. Natural water and diesel are hard to tell apart as they are both usually clear. With a colored diesel, a fuel leak into the water is immediately noticeable, allowing the boat owner or operator to do something about the problem instead of continuing to pollute the waterways. 

Other Alternatives

Biodiesel involves a derivative that is made from organic products versus petroleum. The most common sourcing is from vegetable oil or soybeans. Sometimes it can be made from animal fat as well. It’s not a commonly used fuel as the cost of production is very expensive. However, when it is seen, the color can range from a very bright amber to a boring brown. Again, a lot of the variation depends on what material is left in the diesel after refinement. 

No General Performance Difference

Aside from the grade and refinement, the added coloring to diesel doesn’t signify any difference in performance the way octane in gasoline would flag. However, again, using the wrong diesel on the wrong equipment can result in poorer performance, especially when using a less-refined diesel on high-performance engines. If on the road, assume a clean/clear colored diesel that is taxed is the standard. Colored diesel should be avoided and reserved for off-road or farm equipment instead.

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