Engine Oil overfill

[renos]

I overfilled my 986 S by 0.35-0.40liters of oil.

Is this so crucial so that I will have to take some out? Some people say that it is no problem on a Porsche. However, I know that other cars (Mercedes, VW) have warning stickers all over saying that overfilling can damage the catalysts.

Your views please!

[nick49]

I would crawl under the car and drain a half qt out. This can be done in about the time it took me to make this reply. Not worth the potential problems associated with too much oil.

[Jinster]

What exactly is the problem with a bit over filling? I would've thought car science is never exact. If the tolerance is that exact, then it's a poorly designed car.

[White987S]

What exactly is the problem with a bit over filling? I would've thought car science is never exact. If the tolerance is that exact, then it's a poorly designed car.

And how much is "too much" then? Overfilling is overfilling. This is not good for the car/engine. There are all kinds of potential issues....oil foaming, fouling your plugs, messing-up your MAF sensor(s).

[Jinster]

What exactly is the problem with a bit over filling? I would've thought car science is never exact. If the tolerance is that exact, then it's a poorly designed car.

And how much is "too much" then? Overfilling is overfilling. This is not good for the car/engine. There are all kinds of potential issues....oil foaming, fouling your plugs, messing-up your MAF sensor(s).

Really? Engine oil fouling your plugs and messing up your MAF sensor? Sounds like you got a much bigger problem than just oil overfill.

I would've thought problems would be related to the flow of oil if it's grossly overfilled.

Edited June 22, 2006 by Jinster

[White987S]

What exactly is the problem with a bit over filling? I would've thought car science is never exact. If the tolerance is that exact, then it's a poorly designed car.

And how much is "too much" then? Overfilling is overfilling. This is not good for the car/engine. There are all kinds of potential issues....oil foaming, fouling your plugs, messing-up your MAF sensor(s).

Really? Engine oil fouling your plugs and messing up your MAF sensor? Sounds like you got a much bigger problem than just oil overfill.

I would've thought problems would be related to the flow of oil if it's grossly overfilled.

Hey dude, go ahead and overfill if you want. It's your car & engine.

Oh, one more note, the overfill will mess up your cats. too!

[Jinster]

What exactly is the problem with a bit over filling? I would've thought car science is never exact. If the tolerance is that exact, then it's a poorly designed car.

And how much is "too much" then? Overfilling is overfilling. This is not good for the car/engine. There are all kinds of potential issues....oil foaming, fouling your plugs, messing-up your MAF sensor(s).

Really? Engine oil fouling your plugs and messing up your MAF sensor? Sounds like you got a much bigger problem than just oil overfill.

I would've thought problems would be related to the flow of oil if it's grossly overfilled.

Hey dude, go ahead and overfill if you want. It's your car & engine.

Oh, one more note, the overfill will mess up your cats. too!

Yep. It's my car. And I don't want to overfill it.

No, overfill will not mess up my cat convertor because my engine is intact.

[Rom]

Overfilling by half a quart is significant enough to warrant draining a little out... Overfill causes foaming and aeration which can overheat your oil (damaging the oil lubrication properties), damaging seals, and starving the engine of oil since the aerated oil is harder to pump. Aeration can also lead to oxidation of the oil.

Jinster - I agree with you that engines are not an exact science, but modern engines have far closer tolerances than older engines. For example, just a little excessive fuel into the cylinder can cause bore wash, leading to eventual compression failure. The short-term effects are likely to go unnoticed, but long-term it is not good for the engine.

Slight overfilling is acceptable (say up to 100ml), but half a quart (almost 500ml!) is excessive. That's a 5.7% overfill with filter. So if you just look at the sump (which is where the excess oil will sit), you're probably looking at a 10% (or more) increase in unexpected oil.

I would personally drain the excess oil out.

Thanks!

Shash

Edited June 23, 2006 by Rom

[Jinster]

What you say sounds very sensible, Rom. Thanks.

Edited June 24, 2006 by Jinster

[Donie]

The excess oil doesn't sit in the sump of 986 S........it's a dry sump engine......and the quantity you're talking about here won't cause any problem.

[Rom]

On a Boxster (and 996) they use an integrated dry sump - not an external reservoir. Overfilling the integrated dry sump can cause the oil to overflow into the conventional sump area, which really can't be good. At least with the integrated dry sump the crank can't slosh the oil too much if you do overfill, but I still say that a quart is too much. Case in point, Carlton had oil getting into the intake due to overfilling. Granted he wasn't sure how much excess oil and estimates "a few quarts", but obviously overfilling is bad...

http://www.renntech.org/forums/index.php?showtopic=5972

Thanks!

Shash

[General Eclectic]

I also think a half quart is too much extra oil, even in a sump that large.

The good news is that you don't have to crawl under the car to remove it. A suction gun with a long tube on it will work just fine. The tube goes down the dipstick tube of course.