Will too much oil in the crank damage my motor?

Dear Car Talk

Dear Car Talk | Jan 01, 1990

Dear Tom and Ray:

Could too much oil in the crank case do damage to the motor? I had an oil change on my 1986 Chevrolet Spectrum at the dealer. It started to leak the next day, which it never did before. I took it back after I checked the dipstick, which showed the oil three-quarters of an inch over the full mark. They drained out the excess, but it's still leaking. Do you think the engine was damaged by driving with too much oil?

TOM: If the crankcase was grossly overfilled, it could cause the engine to blow a seal. It could also cause the oil to foam as the engine's moving parts come in contact with the oil. But that would require several quarts of excess oil. Three-quarters of an inch over the "full" mark (probably less than a quart) is not enough to cause any leaking or foaming.

RAY: My guess is that the same ding-a-ling who put an extra half quart in your crankcase, probably forgot to tighten the oil filter or may have cracked or even lost the drainplug gasket. It could still be sitting in the bottom of his pan along with your used oil.

TOM: Take the car back and have them start all over again. Have them drain the oil, tighten the filter, and check the plug gasket for damage. If that doesn't solve your problem, then the oil leak is probably unrelated to that oil change and you'll have to have further diagnostic work done.

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