Question. Does it harm the engine if a person overfills the engine oil by 1 qt? No, I didn't do it, just asking.

It's not good.....however I don't know if it will damage the engine....

I seriously doubt it.

Generally, there should be enough "buffer" room in an engine to handle 1 qt. At some point, overfilling will result in the crank striking the suface of the oil. When that happens, the oil is whipped into a foam. One gets air bubbles in the oil. Oil with air bubbles does not provide the same lubrication to the engine. And so on.

 

It is not a case of 0.95 qt is fine, and 1.05 qt will destroy your engine. If you think about going up and down hills, around corners, etc, you can appreciate that at some point, an overfill will result in occasional striking of the oil surface by the crankshaft. It will get progressively worse at higher oil levels (more overfill) from that point on. At what point this happens in a Subaru engine, or any make of engine, I don't know.

 

Commuter

What would be the effect of oil flowing into the cylinder beneath the piston, like if the car is tipped sideways on a steep hill or slides into a ditch? I've tossed around some airplanes with boxer engines, never really thought about this.

Look at these pics. You're going to really have to over fill it to get the crank whipping the oil

http://www.main.experiencetherave.com:8080/subaru/images/ej22t/2/

Depending on the location of the front and rear seals in relation to the oil level, you could cause some problems with leakage. I don't know if the Subie is subject to it, but my rule is to keep the oil within 1/4 quart of the mark. That's a half quart to play with and should be easy to do.

 

The subies have sufficient oil capicity for the system. There is no reason to overfill.

 

Jack

your dip stick may come blasting out when you start up her up.. if you have THAT much in there... very humorous... if it doesn't happen to you :cool:

It's easy enough to undo the oil pan drain plug for 2 seconds.

 

No more over fill!

 

Just a thought...

Humerous TRUE story: A man in my apartment complex bought his first car at age 58. He knocked on my door and said that the car was making noise. Would I come look? I discovered it was quite low on oil. I advised him to "top it off". The next day he knocked on my door again. The car would not start. I asked him if he had added the oil. He said Yes. I went down to check it out. I pulled the dip stick. The first 18" were covered with oil. I opened the oil filler cap. Engine oil was up to the top of the valve covers. I tried not to laugh. "yep, looks like you topped it off pretty good! How many quarts did it take you?"

Answer: "10"

i have a 05 baja turbo and recently traded my 02 impreza rs both manuals state oil capcity of 4.1qt. but i find i end up putting in 5qts to make my stick read to the full line and sometimes it may be a little over that and i never had a problem with my engine ever. when i put 4 qts in the stick reads low i dont know the reason when the manual states 4.1 to fill.