Rick's Free Auto Repair Advice

What happens if you overfill engine oil?

Drain overfilled engine oil

If you overfill engine oil you can cause serious problems. As the crankshaft spins and comes in contact with the overfilled oil level, it whips air into the oil, creating foam.

Engine oil dipstick showing the ADD and FULL marks to prevent overfilled engine oil

Keep engine oil between the FULL and ADD marks on the dipstick

Engine oil’s job is to reduce friction, prevent corrosion and remove heat. But foam is an insulator, so the oil’s ability to remove heat is compromised and can result in excess engine wear.

Overfilled oil can increase oil consumption and spark plug fouling and catalytic converter damage

If you overfill engine oil, the piston’s oil control rings can drag too much oil into the combustion chamber, resulting in spark plug fouling and excess oil deposits in the catalytic converter.

How much can you safely overfill engine oil?

An engine can typically handle about ½ quart extra. But beyond that you’re looking at problems. If you’ve added more than ½ quart over the recommended amount, drain off the extra oil to prevent damage.

©, 2017 Rick Muscoplat

Posted on by Rick Muscoplat


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