Bad Fuel Kills Engines: A Look Into a Failed Engine


Do you have a can of gas that’s been sitting in your garage since who knows when? If it’s been sitting for over a month, gas can go bad, and using it will stop your car or truck cold!

Fuel goes bad, or fouls, when left to sit for prolonged periods of time. This occurs due to the hydrocarbons in the gasoline either evaporating, or reacting with the oxygen in the air. When this happens, the gasoline starts to form solids called “gum.” Areas with high heat/humidity will increase the speed at which this occurs. Another contributing factor to fuel fouling is ethanol in fuel. Ethanol is hydrophilic, meaning it bonds to water. As it sits in your tank it is attracting and trapping water – this causes further issues down the line.

The story

Here’s an engine we received recently that was exposed to some bad fuel:

What you’re looking at in these photos is the aftermath of bad fuel in a Honda D15B7 1.5L engine. This engine was installed into a vehicle that had been sitting for a prolonged period of time in a high heat/humidity area, allowing the fuel to foul. This fouled fuel caused extensive contamination of the engine, causing valves to stick, which then led to an interference of the valve train and pistons. These valves were so gummed up they required a hammer to remove – yes, a hammer! Further inspection revealed contamination/damage to piston rings, cylinder walls, the pistons themselves and the intake ports.

Keep in mind the contamination you see in these photos occurred during initial startup. This engine has zero road miles on it, and was in brand new condition when installed. Luckily, this customer had our No Fault warranty protection and was able to have this unit replaced under warranty, with parts and labor covered! The vehicle’s fuel system was completely drained/flushed, a new engine was installed and there are no reported issues.

Gearhead Engines strives to build the highest quality products available, but at the end of the day our products are only as good as the installation.

How to Avoid Bad Fuel

Are you looking to make your gas last longer? You can purchase an additive called fuel stabilizer that will keep your gas good for over a year. If your gas has clumps, is dark in color, or has a stale/sour smell, it’s probably gone bad. Bad fuel can be dropped of at your local hazardous waste disposal center.

Have questions? We’re here to help. Give us a call at 800.508.5999.

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