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Overfilled Oil Change

When my mechanic does an oil change, he routinely overfills the oil by about 1/2 to 3/4 quart. The dipstick measure about 3/4" above the full mark. He says engines burn oil so he overfills the oil. Is this harmful to my engine? If so, should I have some oil removed.

I don’t think that a “small” amount of overfilling oil will do any damage. The problem is that all engines are not the same. If your daughter experiences oil leaks then her engine is probably suffering the effects of overfilling. I personally never overfill anything because there is always a chance of doing damage. Is your daughter going to a real mechanic or to one of those “quickie change shops”? There are no mechanics at a quickie shop so they should always be avoided. No filling, underfilling and overfilling are their specialty.

A small amount of extra oil won’t hurt anything. Does your engine burn a bit of oil?

I do not believe all engines burn oil. Many do, but not all.

The mechanic is likely making up this story, since he likely has a number of full bottles of oil an most cars do not take an even number of bottles.

He is supposed to fill it to the factory designated level, and give you whatever is left over in the bottle to take home. But that takes work, and some thinking so he does not bother.

As others say, 1/2 quart is no big deal in a Taurus engine, 3/4 of a quart leaves me puzzled. He would have been better to UNDERFILL it by 1/4 of a quart and charge you less.

If he overfills out of the bulk tank, he is really out to lunch (cars usually don’t consume much oil), unless he is trying to charge for an extra quart. I would go to another mechanic.

How many quarts is being added?

Just tell him to add the correct amount of oil and promise that you will check it regularly. (But then you have to keep the promise).

They’re supposed to give you the leftover oil to take home? Really?

I guess it really has been a long time since I’ve had my oil changed by someone else. At least since before they had 5-quart bottles.

Hey, howcome they didn’t start packaging oil in 5-quart bottles until most cars had switched over to 4-quart systems?

I agree that a small amount over in a Taurus is not harmful, but overfilling is also not a good idea as a standard practice. I have to wonder about this practice.

Disclaimer - I really don’t know :slight_smile:

But my dad told me it was worse to overfill than to under-fill a little. His reasoning was that added pressure would be put on the engine seals. Makes sense to me, and certainly doesn’t hurt to be careful not to overfill.

When I discovered a year or so back that my local tire shop, who did the cheapest oil changes in town ($24) was overfilling my vehicle by 3/4 qt each time, I started doing it myself again.

I also decided to start using full synthetic, which would make it a lot more costly to pay someone else to do the work - at least that way I felt better about having to do it myself again after a few years of feeling rich. :slight_smile:

Yes, my service station will fill the crankcase to the exact full level and the 1/2 bottle left over will be put in a plastic bag and left on the floor of the car.

The rapid service in my area ( good, not a Jiffy Lube) ) has a computer program that scans the VIN and then has the precise amount delivered through the hose if you buy bulk oil. No possibility of mistake, and they inspect the underside to make sure the plug or filter do not drip, as well as checking the dipstick.

I agree with your dad. I’ve seen oil seals fail because of overfilling.

And, I have a 2000 Ford Explorer, 193,000 miles on it, and doesn’t need extra oil between oil changes every 6 months (about 5,000 miles). May it burns 1/4 of a quart between changes.

I don’t agree at all the the quanity of oil (in this case a small amount overfill) will increase oil pressure. Now if we are talking about crankcase pressure this would take a double shot of oil to do that.We would see high crankcase pressure due to the quanity but low gallery pressure due too “foaming” of the oil. Overfill "a little’ underfill "a little’ no harm what so ever.

Now we certainly can reach a point (different with each engine and operating parameters) where overfills and underfills will cause harm in equally destructive but different ways.

That small amount of overfill will hurt nothing.

Now if you start talking about overfilling one to the tune of 3 or 4 quarts then you may have problems.
I consider a small overfill like this as “extra engine insurance”. Better 3/4 over than 3/4 under.