What Is Dry Gas and Should You Add It to Your Gas Tank?

Reviewed by

Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Written by CarParts.com Research Team - Updated on December 17th, 2024

Reading Time: 4 minutes
Summary
  • Dry gas is an alcohol-based fuel additive containing isopropyl or methanol.
  • Alcohol can be corrosive, and non-flex fuel systems aren’t built to handle it, so using dry gas depends on your vehicle.
  • Your vehicle might develop rust and driveability issues if you use bad gas.

It’s always a good idea to protect your ride’s fuel system and ensure its fuel is contaminant-free. That means buying gas from stations that sell a lot of gas, primarily. Low volume gas stations sometimes have water in their storage tanks. Water can also enter gas station storage tanks if they’re not properly closed after being refilled by the tanker truck.

After all, it isn’t uncommon for water to get into the gas tank. Good thing additives like dry gas can help solve the problem, but you might have to think twice about adding it to your tank.

What Is Dry Gas?

Dry gas is an alcohol-based fuel additive that contains isopropyl or methanol. Alcohol is hygroscopic, which means the additive can bind with water. Dry gas mixes with the water contaminating the fuel so that it will burn along with the fuel during combustion.

This property of alcohol is one reason water is used with a graduated container to determine alcohol content of the fuel. Flex fuel vehicles are designed to run on up to 85% alcohol, but most people who drive flex fuel vehicles never use E85 fuel even if it’s available at the pump.

Dry gas is an alcohol-based fuel additive that contains isopropyl or methanol.

Methanol also has a low freezing point, making a dry gas additive work as an antifreeze during winter. Gasoline can freeze, but usually it won’t. But adding too much alcohol to a non-flex fuel vehicle can cause very annoying driveability issues.

Is Dry Gas Good for Your Car?

It depends on the vehicle. Alcohol can be corrosive, and non flex fuel systems aren’t built to handle it. Flex fuel equipped vehicles will have more robust components than non-flex fuel vehicles for that reason.

High amounts of alcohol can damage the plastic or rubber material in the fuel system. So it’s best to consult a knowledgeable mechanic before pouring dry gas additives into your fuel tank. Typically, additives like this are used as a remedy rather than a preventative.

If a vehicle always stumbles during sharp turns, it can indicate that there is some water sloshing around in the fuel tank getting picked up by the pump.

How Does Water Get Into the Gas Tank?

Condensation happens on the inside walls of most any gas tank that is always running low on gasoline. Keeping the tank mostly topped (½ tank or more) if you only use the vehicle in town will help prevent condensation within the tank. This problem is worse in areas with high humidity.

Keeping the tank mostly topped (½ tank or more) if you only use the vehicle in town will help prevent condensation within the tank.

Richard McCuistian, ASE Certified Master Automobile Technician

Water can get into the tank during heavy rains if the gas cap is damaged or lost, and leaks at the fuel pump can also cause water contamination. Take note however that leaks around the fuel pump are extremely rare, and on OBD2 equipped vehicles, you’ll typically have an EVAP system code stored if there’s a leak around the cap or the pump.

Older style fuel pumps tend to have a bit of space between the sock filter and the bottom of the tank. | Image Source: Richard McCuistian
Vehicle fuel tanks up until the ‘90s tended to have their pump intake sock an inch or so off the bottom of the tank, which enabled water to gather over time so that there might be as much as a gallon of water in the tank just from condensation. | Image Source: Richard McCuistian
Newer fuel pump assemblies are spring-loaded so that they’re firmly against the bottom of the fuel tank. That way, any fuel tank condensation can be handled as soon as it begins to form. This prevents too much of it from gathering in the tank. | Image Source: Richard McCuistian

What Happens When Water Contaminates Car Fuel?

Bad gas (or contaminated gas) can have detrimental effects on your engine. Here are some of them:

Rust

Moisture can cause the metal parts of your fuel tank to rust. That being said, most modern vehicles now have plastic fuel tanks, so tank rust isn’t always an issue, but fuel pump issues can be, particularly if the vehicle is parked for a week or two and water is in or around the fuel pump.

On vehicles with steel tanks, rust can reduce the thickness of its lining and cause fuel leaks. At that point, nothing short of replacing the tank could fix the problem.

Driveability Issues

Contaminated gas can cause driveability and performance issues. For example, your vehicle can have a hard time accelerating when its fuel is contaminated with water because the moisture can reduce combustion. Excessive water in the fuel system can also cause your engine to stall.

Many fuel additives can improve the health of your vehicle in general. Although experts recommend a lot of these additives, make sure to read up on the chemicals they contain before adding any to your gas tank.

About The Authors
Reviewed By Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Written By CarParts.com Research Team

Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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CarParts.com Research Team and Richard McCuistian, ASE Certified Master Automobile Technician