Problems Caused by Engine Oil Overfill

by Jen Davis
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black car image by Viachaslau Makouski from

Car engines are designed to run on a specific amount of oil. Too much or too little oil can adversely affect the vehicle's performance and reliability. Most people know that running an engine low on oil is a bad idea and can cause serious damage to a car or truck. However, many owners don't realize that overfilling engine oil is just as problematic and can cause engine problems or complete engine failure over time.

Aerated Oil Problems

When you put too much oil in an engine, there is nowhere for the excess oil to go. As the oil is turned by the crankshaft, it can become oxygenated and assume a foamy quality. Oil mixed with air does not lubricate as effectively and tends to cause overheating as well as damage to the engine's moving parts. The vehicle may experience loss of oil pressure because aerated oil is difficult for the oil pump to process.

Seals and Gaskets

Overflowing engine oil can cause various seals and gaskets to fail as the excess oil is forced out of the engine. As seals and gaskets fail, the vehicle will develop oil leaks, which can leave unsightly stains on a driveway as well as produce low oil levels in the engine, causing further damage. Blown seals and gaskets must be detected and repaired.

Combustible Fumes

If there is enough extra oil in the crankcase, it may be forced out through the piston seals and rings as the vehicle runs. This creates "blow-by," which has the potential to coat your engine in oil. As the oil burns off, noxious fumes and gases are released. This can create a fire hazard if enough oil accumulates on the outside of the engine.

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