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What Color Is Gas Supposed To Be? (Signs That It’s Bad!)

What Color Is Gas Supposed To Be? (Signs That It’s Bad!)

It’s important that to be able to differentiate the color between good and bad gas. When a fuel tank is full of bad gasoline it can cause all kinds of damage to your vehicle.

Natural gasoline has no color at all and is clear like water. However, each grade of gas is dyed with sulfur or other dyes in order to differentiate the fuel for various types of vehicles or octane levels. Dark brown or black gas is indicative of a problem.

When the fuel has been sitting in a gas tank for an extended period of time, then it is important to check its color. Gas should not be a dark brown color, because that means it has been stagnant for too long and has become oxidized.

It’s important to know what you should do if you come across bad gasoline in your fuel tank.

Different Grades and Colors

Pure gasoline is a crystal-clear color, which has a basically identical appearance to water. This has made it hard for sellers, manufacturers, and consumers to differentiate between the different grades of fuel.

For this reason, manufacturers have changed the colors of gasoline to help differentiate the fuel types! The different grades of gasoline are often dyed with sulfur or other additives.

The main petroleum-based fuels that are used in vehicles are:

  • Regular (87 Octane)
  • Midgrade, also known as Plus (89-90 Octane)
  • Premium, also known as Super Premium (91-94 Octane)

Regular gasoline usually has a green or bluish hint to it. This is sometimes confused with the bluish color of aviation or racecar fuel.

Midgrade or Plus gasoline usually has a yellow color.

Premium gas is often a pinkish color.

No matter what the gas color may be, it should still be transparent and light in color overall.

When initially pumping gas in a fuel tank, it’s not too crucial to see which color it is (and it’s difficult to check the color at a gas pump anyway). The dyes are mostly to help the manufacturers and sellers differentiate between the different gases.

If you haven’t driven your car for a while (about a month or longer) it’s important to check its color. If it is a dark brown color, this means that the gasoline has oxidized and is potentially dangerous for your vehicle.

In order to compare the colors of gasoline, you can pump some fresh gas and some old gas into two transparent vessels. The fresh gas will be light in color and will depend on the fuel type that you have chosen.

If the older gas is a much darker brown than the fresh gas, that means that the oxidized fuel should no longer be used.

Dark brown gas can cause vehicles to stall, slowly accelerate, delay gear shift, and can even cause the check engine light to illuminate. Using oxidized fuel can create costly and irreversible damage to the vehicle, so it is important that you know between the fresh and expired colors of gasoline.

How to Remove Oxidized Gasoline

It is always wise to seek help and advice from a professional, rather than taking this task into your own hands. However, if the situation does not allow this, there are instructions on how to remove bad fuel on your own.

If you see that you have oxidized gasoline, you will want to remove it from your fuel tank. If the fuel tank is full of expired gas, it may take a longer time to empty because it can take up to two minutes to siphon out one gallon of gas. Be sure to set aside some time to pump out bad fuel.

Also, ensure that you are in a well-ventilated area before performing a fuel tank drainage due to the dangerous vapors of gasoline.

First and foremost, it is important to have a siphon hand pump available. It is hazardous to inhale or swallow gasoline, so be sure to utilize a siphon hand pump.

This is a small tube that will be used to pump the gas out of the fuel tank. It should be about 6 feet long and 3/8 inch to 1 inch thick (the thicker the hose, the longer the pump time will be).

Another item you will need is fuel storage can in order to store and dispose of the oxidizing gas. Using the hand pump, you will feed the siphon hose into the fuel tank.

Once you have reached the fuel tank, you will feed the other hose into the fuel storage can and pump out the gas until the fuel tank is empty.

When all the bad gas has been siphoned out of the fuel tank, it is crucial to dispose of it in a government-approved site. Gas should never be thrown away in trash cans, drains, lakes, etc.

Be sure to contact your local waste department to ensure you’re using a proper disposal site.

Gasoline Shelf Life

The shelf life of gas isn’t very long. It lasts anywhere between 3-6 months. Once reaching its expiration date, gas oxidizes and becomes highly unusable.

Unfortunately, the higher grade fuel types do not have a longer shelf life than the regular gasoline.

However, there are a few ways to extend the lifetime of gasoline. There are fuel stabilizers up for purchase that can slow the time that it takes for gas to oxidize. The most popular brands of fuel stabilizers are STA-BIL, Seafoam, Lucas, and Marvel.

Fuel stabilizers and additives are best to use in new gas so they can offset the effects of oxidation, but it won’t be much help for gasoline that has already oxidized.

Using a fuel stabilizer can keep gasoline fresh anywhere from 1 to 3 years.

If you do have old gas in your fuel tank, you also have the option to dilute it with fresh gasoline. The combustion ability of the car might not be up to par, but it allows you to utilize the old gasoline.

When doing this, it is important to contact a professional to see if you will need to add any fuel additives to the fuel tank.

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Zach Reed

Hi, I'm the founder of! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!