What are the consequences of overfilling the oil?

[PabloX]

I recently completed replacing all the oil return tubes on my '86 3.2. In retrospect, I probably should have drained all the oil beforehand but I didn't, as the car had an oil change not long before that.

The problem now is that I have no great idea how much oil is in the car. I'll take a wild guess that somewhere around 4 to 6 qts came out when I took out the old tubes. So at this point do I just drain the whole thing and waste whatever quite fresh, expensive synthetic oil is in there? Or, do I put 6qts in and run the risk of overfilling?

I guess another way to ask this question is what's the minimum amount of oil in the car where it's safe to run the engine (since the car needs to be warm to really check the oil)?

[porsche930dude]

id say put a couple quarts in and slowly fill as needed. you dont want to overfill it. it gets in the intake and gunks everything up

[PabloX]

Originally Posted by porsche930dude

id say put a couple quarts in and slowly fill as needed. you dont want to overfill it. it gets in the intake and gunks everything up

Thinking about it a little more, it would seem I lost most of what was in the crank case but the oil tank should have been unaffected. Does that make sense?

[AlfonsoR]

I believe the oil in the tank does get affected, but no idea by how much.

Another idea is to measure what you've drained. Otherwise if that is not possible, do you really want to risk reducing the life of the bearings?

[porsche930dude]

or you could just drain it into a clean container and pour it back in. that shouldnt be too difficult to keep it clean

[Hnichols]

Why can't you just fill it slowly until it registers on the dipstick. Then spin the motor (with fuel pump fuse removed so it doesn't fire) which will suck oil from the tank, then add a little more oil, start the car, make sure you have enough pressure, drive it until it gets to temp, and then fill until it above the first mark on the dipstick.

[Canada Kev]

I think registering on the stick with the car cold and not running is over filled.

If you don't know how much you lost, then it's probably best to drain what you have into a clean container to measure, and then add that back in. If you think you're down only about two or three quarts, you can get away with running that until it's hot to check the oil. The system capacity is quite large, and even the difference between the lower and upper mark on the dipstick is 1.75 quarts.

[ant7]

+1

Originally Posted by canada kev

i think registering on the stick with the car cold and not running is over filled.

If you don't know how much you lost, then it's probably best to drain what you have into a clean container to measure, and then add that back in. If you think you're down only about two or three quarts, you can get away with running that until it's hot to check the oil. The system capacity is quite large, and even the difference between the lower and upper mark on the dipstick is 1.75 quarts.

[Dodge Man]

I had a 73 MFI car come into the shop where I worked as a teen with just 3 quarts in the sump. Motor was fine so be happy about your Porsche dry sump. Owner was used to US cars and said the alternator light was flashing(parking brake). Years later, I had a body shop overfill my 911 because the oil light flashed when the parking brake was up and made a mosquito killer until I drained the case of 3 quarts and cleaned the CIS air box. IME Yes, overfilling is very easy to do. Happy cleaning.

[bcoats]

If I remember correctly, I believe there is about 3 quarts in the sump, I think adding 2 to start should be safe and add when registers on the dip stick

[matt gineo]

It's very easy to stick a tube from a manual oil evacuator pump into the oil fill tube and suck out any excess oil. I did this on my Targa when I first discovered that it was overfilled by the previous owner. We use these type of manual pumps when changing oil in our boats because you can't get to the bottom of the engine to drain it. You simply stick the pump tube into the dipstick tube and pump out the hot oil. Amazon.com: Mityvac 7400 7.3 Liter Fluid Evacuator: Automotive

[howard freeman]

Drain it all out & start over. Get rid of the low zinc synthetic oil & use either Valvoline VR1 ,Brad Penn, Joe Gibbs Driven DT40 or Motul 8100Xcess. Your cams will be very happy.
Howard

[PabloX]

Originally Posted by howard freeman

Drain it all out & start over. Get rid of the low zinc synthetic oil & use either Valvoline VR1 ,Brad Penn, Joe Gibbs Driven DT40 or Motul 8100Xcess. Your cams will be very happy.
Howard

I ended up draining it and starting over.

FWIW, the oil is Mobil 1 15W-50, which is pretty close in zinc content to those you listed.

[CountD]

Originally Posted by PabloX

I ended up draining it and starting over.

FWIW, the oil is Mobil 1 15W-50, which is pretty close in zinc content to those you listed.

I personally would not use Mobil 1 in a 911 engine - ever. Second thing, and I think most people covered it, if it's overfilled (my experience) it gets in the intake, and not only that it sprays the whole engine compartment. The past owner of my car overfilled the engine every time, and it took days to clean the engine (not to mention the huge puddle of oil in the CIS intake that looked to have been there for years as it was pulled in and refilled with oil).