What can too much oil do to an engine

Dear Car talk I just had my oil changed by a professional shop, just for grins I checked the level and found it to be way too high; so go back to the place and another oil tech checks the level and says yes it is way too high; they emptied out and put in a new batch of oil; my question is I was driving around for about 2 weeks like that; what is the chance of any mechanical issues and should I pursue A letter the upper management about techs doing the double check of the oil level, which this one did not do. thankyou for your time. Frank

Have to wonder HOW it got that way. Was it because they just added too much oil…OR they added the correct amount but DRAINED the tranny instead???

What do you mean by “Professional shop”??? If you mean something like “Jiffy Lube”…Sorry but they are NOT very professional as far as I’m concerned.

IF they did drain out the old oil and just overfilled by a couple of courts…then there probably isn’t a problem. But I’d take it to a PROFESSIONAL MECHANIC to make sure…

First, we need to ask, "How high is too high?"
Generally speaking, 1 qt over the “full” mark on the dipstick is not problematic. Of course, this is a generalization and it is possible that some engines would develop problems with just 1 qt too much oil.

If a crankcase is overfilled, the result is that the crankshaft churns the oil into a froth. This froth, when carried by the oil pump to sensitive bearings, does not lubricate the bearings as liquid oil would. The result is bearing damage.

How long would it take for this damage to occur? I can’t really answer that question authoritatively, but I will share my own limited experience with the issue. About 3 years ago, about 5 days after an oil change, I finally got around to checking under the hood. (I normally do this right away, but on that day I became occupied with other emergent situations.) To my shock, I found that the level of oil on the dipstick was waaaay over the full mark, and I would estimate that it had about 2.5-3 qts too much oil.

I drove directly back to the dealership, where they drained the oil and refilled with the correct amount. While I was apprehensive about the long-term effects, the service mgr stated that he did not anticipate any problems, but would stand behind their work if any problems developed. Still, I was apprehensive.

Approximately 3 years later, with about 103,000 miles on the odometer, my engine still burns absolutely no oil between its 4,000 mile oil changes and it exhibits no problems whatsoever. Was I lucky? I’m sure that I was. Most likely just a bit more oil would have raised things to the critical level.

I think that the amount of excess oil that would cause damage is something that would vary somewhat from one engine type to another, but I can report that the Subaru H-6 engine can withstand 2.5-3 qts excess oil for several days without damage.

How the engine in your mystery vehicle will fare is an unknown, as is the exact level of oil that was in its engine. Would you care to give us more details?

Edited to add:
The reason for the overfill of my crankcase was a defective metering device. This device, which was supposed to meter the correct amount of oil from the bulk barrels at the dealership, was at least 20 years old, and was really screwed-up by that time. On my next visit, the service mgr showed me the new metering device that they had obtained from Valvoline. Now, no more mistakes. Apparently I was not the only one whose crankcase was overfilled by the old metering device.

Too much oil depending on sump and engine will cause less than optimal lubrication as the oil gets whipped into a froth/foam. However if no weird/odd noises I would not worry much about it.

Stuff happens…

A quart or two over won’t hurt anything although this should never have happened. It’s incumbent upon the shop to double check the oil level and inspect for leaks after performing an oil change.

This is not by chance a Subaru is it?