Can too much oil damage your engine ????

tjflaher

Can anyone out there tell me what is the first thing damaged when you drive with too much oil. When the engine is cold now it raps until it warms up. Is this the valves, guides, seals or something ?

See Also: Stop Changing Your Oil!

oldharry

If the oil level is too high, it contacts moving parts in such a manner as air is mixed into it. The result is air pockets oil galleries, and less liquid oil to cool parts such as piston skirts. The "foam" also sticks in place and doesn't drain back to the pan, and insulatesparts from normal heat transfer.

In other words, if you ran too much oil too long, you have trashed your engine.

Harry

oldharry

The knock until warmed up is likely piston slap. The piston skirts are worn or distorted from excess heat.

Harry

Mr_Shiftright

I'll offer a little less pessimistic opinion on that. Too much oil will probably damage seals before anything else, but cavitation is possible. I've never seen or heard of a street engine used in normal conditions self-destruct from too much oil. I'd say it was highly unlikely but I'm not ruling it out.

Your noise could be piston slap or it could be a sticking hydraulic lifter or it could be a loose wrist pin. There are other possibilities as well but those are most likely.

tboner

I'm pretty sure you can get to a level of overfill that will damage any engine.

The above comments are spot on, seals and the oil being turned to foam by the crankshaft are issues.

However, with that being said, I run about a pint of extra oil in my SVT Contour, could probably run a bit more.

Why? Well most of the driving is at higher RPMs, and this is a DOHC engine, so by the time the engine gets running, there is at least a pint of oil in the heads.

So, when I'm charging those 40MPH exit ramps at 80MPH (when I can safely do so) I don't worry about my oil pickup sucking air instead of oil.

(That will certainly lead to a catastrophic failure if it goes on for any significant length of time.)

But for 99 and 44/100ths percent of all people, you want to run the recommended oil volume and no more.

TB

Mr_Shiftright

It would be an interesting experiment on a junker engine at a wrecking yard. Fill that sucker up with ten quarts and floor it. I know for sure it would be a mess but I'm skeptcal the engine would destruct. Anyway, I really don't know, just an opinion. Certainly it's not a good thing.

csandste

Bought it for her used. 100K on Mobil 1. Noticed that she wasn't checking her dipstick, oil was low. Decided that the easiest thing to do was add a quart every time she filled up. Had so much oil (probably about 7 or 8 quarts) in there that it blew out a spark plug. Impressed upon her that too much oil isn't a good thing. Engine had terrible blowby, but it's still going strong at 200K. I still have heard the air in the oil story and wouldn't totally discount it.

swschrad

that means the engine just barely avoided hydrolocking. that busts just about everything inside that moves.

dustyk

...and heard of a few more blown from too much oil. The first was a '58 Oldsmobile with about 6,000 miles and about 8 quarts of oil. The entire under carriage of the vehicle was coated with oil from the blow-by tube. This engine did not run very well. There is a terrific amount of load incurred from eight connecting rods swinging through 4 inches of oil. After being driven for about 25 miles, excessive air bubbles in the oil finally took its toll on the rod and main bearings. It's probably hard to believe but this engine seized.

The other was a '90 or '91 350 Chevrolet marine engine (in a boat, of course). I am not really sure how much oil was in the engine. It was hard to tell since about a 7 inch round hole was punched through the side of the block between number 5 and number 7, caused by number 6 breaking off at the very top of the rod. Another piston had begun to separate at the top ring groove. When we got the engine out we noticed that one of the block bulkheads was cracked from the main bearing cap almost all the way to the top of the crankcase cavity.

Yes, too much oil can blow a engine.

Dusty

desi501

I would say that small amounts of overfill (1-2qts) will cause mainly oil leaks. It will come out orifaces that you never knew you had. If you go beyond a couple quarts over, now anythings possible. Those moving parts need some space to move. If they don't get it, they will make room.

chris_horne

My experience has been that a small amount of overfill (<1/2 quart over) will not hurt anything. In fact, I have read of LS1 Camaro owners overfilling by 1 quart to increase their oil capacity.

It reaches a point though, where the oil reaches the height of the rotating crankshaft, and this whips the oil into a froth. Oil with lots of air in it does not lubricate well. The result can be the same kind of problems you wuold have running a car without oil...e.g. bearing failure, catastrophic damange.

I personally am not familar wtih leaks resulting from overfilling. Can anyone who has seen these first hand please give us any details. How much oil are we talking about?

desi501

You go beyond the fill level and you open yourself to all kinds of things. Do you think the engineers just blew it and made the level too low.The pan has baffles that are designed around the normal oil level. When you go above that you create all kinds of splash and foaming that's not normal. If you want to increase your oil capacity, then you have to make the oil pan deeper. A half quart is probably not a big problem, but why? The engine is engineered to operate on a specific amount of oil, why change that? Extreme heat or racing conditions, OK, enlarge the pan. Otherwise the factory knew what they were doing. Nothing good can come from overfilling.

dustyk

...is required when an engine can go from low RPM to very high RPM is such a short time that the oil in the oil pan is pumped out before the flow-back oil can return back to the pan. In some racing engine applications, its to ensure enough oil is covering the pump inlet on high-G turns.

For the vast majority stock automobile engines this will never be a problem. As someone has already indicated, the engineers who designed the engine probably knew what they were doing. Overfilling any engine beyond the recommended level could be perilous. It most certainly isn't going to provide any margin of protection for a factory engine driven on the street.

Regards,
Dusty

chris_horne

I don't think this happens by plan, but oil change places are of course in a hurry to get the job done, and they do not take the time to let the oil drain out completely. Then they fill it to the capacity stated in the owner's manual. The result is a slight overfill.

I was visiting some people in FL and took my car to a quick change place. They gave it back to me somewhat above the full mark. I complained loudly and even called the owner, but they would not take the time to adjust it. Called the service manager at my GM dealership in PA, and he said...a little bit over is not going to hurt anything, so I just let it go.

I am now changing my own oil, so this is not a problem.

chris_horne

Another reason why --> Some cars take fractional quarts of oil. For example, my Lumina takes 4.5 quarts. I have heard of people who will just use the entire container rather than keeping 1/2 quart on hand.

I am not recommmending such practice...just answering your question of "why?".

desi501

A half quart isn't going to kill you but it still isn't recommended to do intentionally. chris_horne was right. It happens because nobody ever looks for the EXACT capacity. They just fill till it looks full. Just lazy.