Many of us don’t think about the color of gasoline because we never see it — we put the pump in our car, turn it on, and the gas goes straight into the tank. But if you’ve ever spilled gas, you may have noticed it has a slight tint to it. What color is gasoline, really?
Gasoline is clear or slightly yellow. However, some refineries may tint their fuels before distribution to differentiate between different fuel types. Each country has its own regulations for fuel dying. In the United States, fuel for off-road vehicles must have a red tint.
Though most gasoline is clear and yellowish, it’s helpful to know what the colors mean if you stumble upon dyed fuel. Keep reading to learn more about what the different fuel colors mean.
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How Fuel Is Colored
Depending on the refinery and the specific refining process used, gasoline may be clear or have a yellowish tint. Often, this is the color you’ll find at the pump. However, some companies may prefer to dye their fuels. In general, the colors of each fuel type are standardized throughout the United States, even though there is no regulation for most fuel types.
Gasoline Colors
When regular gasoline is dyed, manufacturers will color it according to its octane grade. Most pumps will offer “regular” and “premium” gasoline, and some pumps will have a “midgrade” gasoline as well.
Regular gasoline, also called unleaded gasoline, typically has an octane rating of 87. When dyed, it’s often given a bluish or greenish hue.
Midgrade gasoline is also sometimes called super unleaded gasoline. This gasoline’s octane rating is usually somewhere around 89-90. Midgrade is created by mixing regular and premium gasoline, and it may have a yellow tint.
Premium gasoline, or super-premium unleaded, has an octane rating of 91 or above. Manufacturers dye premium gasoline pink.
Octane Ratings Explained
The octane rating of gasoline measures how likely it is that the gasoline will ignite prematurely. The higher the octane number, the more stable the gasoline, and the less likely it will combust at the wrong time.
When gasoline is first refined, it has a rating of about 70. To increase this number, refineries will further process or add elements to the gasoline. For an unfortunately long time, the preferred element was lead. When we discovered that having lead in the atmosphere was not the most healthy thing in the world, the switch was made to other elements such as ethanol.
Diesel Colors
In general, diesel, like regular gasoline, will also be clear or yellowish, though sometimes companies will dye it green. Specific types of diesel may be dyed red or blue depending on their use. The coloring of diesel fuel identifies it as tax-exempt.
Red diesel is for off-road vehicles. This often includes things like boats, construction equipment, and farm equipment. As it’s not for use on the road, it is tax-exempt.
Blue diesel is meant for government vehicles and isn’t available to the public. As they are for government vehicles, they are also tax-exempt.
If you’re supposed to be using clear diesel and red diesel is found in your tank instead, you can be subject to stiff penalties depending on where you live.
Why Fuel is Dyed
There are few regulations and few set standards for fuel dying, and it may not be clear at first why companies would choose to do so. There are a few reasons a company may opt to dye their fuel:
- To identify fuel types. When each type of fuel is a different color, it’s easier to differentiate between them in case of a mixup or missing labels.
- To identify contamination. Unfortunately, a gas spill or leak can cause gasoline to contaminate the local water supply. Dyed gasoline is much easier to detect in water. Undyed gasoline will blend in, meaning gasoline can only be identified by smell or by testing. Dyed gasoline will tint the water, allowing for visual confirmation of contamination.
- To identify tax evasion. As mentioned above, tax-exempt diesel is red or blue. Some may be tempted to use tax-free red diesel instead of regular diesel, but this will only put you at risk of receiving a hefty fine. The IRS is allowed to check highway vehicles and issue steep fines to violators.
How To Tell if Gas Has Gone Bad
Over time, gasoline can go bad because of oxidation or water contamination. When this happens, it no longer works the way it’s supposed to. If the gas is already in your car, the only way you might know it’s gone bad is if your check engine light comes on or if you experience engine problems.
However, if you store your gasoline, there are two ways you can tell if the gasoline is off: color and smell.
When gasoline goes bad, it shifts from being transparent to murky. The color will darken as well. Undyed gas turns a dark gold color, similar to apple juice. Dyed gasoline will become a darker shade, like a teal or reddish color. Dyed diesel may appear brownish.
Because the chemical composition of the gas is eroding, the smell also changes. Bad fuel will smell sour, almost spoiled, instead of having the typical gasoline smell.
Other Fuel Types and Their Colors
Most fuel is clear or slightly yellow after the refining process and, as we just saw, companies may choose to dye gasoline for easier identification.
However, gasoline and diesel aren’t the only fuels that are typically dyed.
Aviation Gasoline
Aviation gasoline is the only fuel type that has worldwide regulations for color. Like regular gas, the color identifies the octane rating and type.
Jet Fuel
The jet fuel used in a standard commercial airplane is kerosene-based and available in two types, Jet A and Jet A1. The differences are in composition and freezing point. Jet A is typically used in the U.S., while the rest of the world uses A1. U.S. flights may use A1 for international flights or for flights over polar routes, as A1 has a lower freezing point. Both types are clear and not dyed.
AVgas
Aviation gasoline is for small-piston engines, the type used for hobby flying, training, or by private pilots.
While regular car gasoline no longer uses lead as an additive, AVgas still does. The more lead in the gasoline, the higher the octane rating. Each octane rating has a different color.
The most common AVgas types are AVgas 100 and AVgas 100LL. The L.L. in 100LL stands for “low lead,” as 100LL has less lead per gallon than AVgas 100. 100LL has 1.2-2.0 mL of lead per gallon. This is the most commonly used type of aviation gas, especially in North America and Western Europe. The dye in 100LL is blue.
AVgas 100 has, for the most part, been replaced by 100LL. Colored green, AVgas 100 has 3.0-4.0 mL of lead per gallon.
The availability of AVgas 80/87 is limited, but it does still exist. With only .5 mL lead per gallon, this AVgas is red.
While it’s unfortunate that lead is still being used in AVgas, the U.S. Federal Aviation Administration is working toward finding alternative additives.
Kerosene
Kerosene is another type of fuel created by refining crude oil. Kerosene is used to make jet fuel, heat homes, and for use in portable devices like camping stoves. Like gasoline, kerosene is clear when refined. However, most kerosene you can buy in stores today is red. Like diesel fuel, the red means it isn’t taxed.
How Cans Are Colored
When you buy fuel in a can, you’ll notice each type of fuel is in a different color can. Red, blue, and yellow cans are for flammable liquids, while green denotes combustible liquids. The colors each represent the following liquids:
- Red is for gasoline.
- Blue is for kerosene.
- Yellow is for diesel.
- Green is for oils.
How Pumps Are Colored
While not all gas stations color-code their pumps, many do. This helps consumers avoid mixing up diesel or ethanol gas with regular gas. While not every gas station is the same, in general, pumps are color-coded like this:
- Green pumps are for diesel gasoline
- Yellow pumps are for E85 gasoline or high-ethanol gasoline
Other colors, such as black, white, and red are used for regular gasoline. Some gas stations may color-code each different octane rating, but not all do. It’s essential to pay attention to the color pump you’re using. Diesel and high-ethanol gas should only go into engines designed for those types of gasoline.
Conclusion
Gasoline and other fuel types are clear or may have a slight yellow tint after refining. However, some companies may opt to dye their gasoline to distinguish between different octane ratings. Gasoline usually takes on a darker color after going bad.
Diesel is dyed red or blue to distinguish regular diesel from tax-free diesel. The only regulations for dying fuel in the United States are for airline fuel and diesel and kerosene, which are tax-exempt.