pp000830

Excessive Oil Consumption and its attendant poor running, is a major reason owners consider a top-end rebuild under the assumption that the valve guides are worn to the point that excessive oil is slipping past them and burning. The logic in this seems sound.
Then again I recently ran across the following shocking comment in the 993 Rennlist Forum in reply to an oil consumption concern thread:
The implication here is that a true measure of a full oil tank is somewhat variable and overfilling may be contributing to the perception of excessive oil consumption where none may exist, go figure?

vincer77

Yes. I have experienced this phenomenon.

Drisump

I'm sure I'm not telling anything that many others don't already know but on both my 911's, a 3.2 and a 993, if I make a mistake and fill to the full mark, both will consume oil quite quickly, until about halfway between hi and low. If I fill to mid mark and aim to maintain between low and mid mark, I will go thousands of miles between quarts. BTW the 993 dipstick is easily the worst I've ever seen...probably Porsche trying to make the driver go to a Porsche centre to have his oil checked....LOL. Of course on a OBD2 car with SAI, minimizing your consumption of oil is very important otherwise dealing with the SAI issue is in your future. Cheers

frankv

This oil level thing has taken a while for me to understand with my particular car as well. At first I thought I had excessive oil consumption as I could easily be adding a 1/2 liter (quart) every other fill up or so and the car would happily guzzle it down the dipstick. However with some experimentation I have figured out that my car is happiest with the oil level just below the level that the dipstick can read. I have gone months and thousands of miles now without adding oil and yet I know whenever I add about a 1/3 of a quart it will mark the bottom of the dipstick. Anything more than that seems to disappear by the time I next fill-up.

I trust what the car is telling me more than what I should be reading on the dipstick

Dan V

I agree although in my case I substitute "oil gauge level" for "oil tank".

KeninBlaine

Interesting discussion. I've only had my 993 C4S for about 6 weeks, and find the oil level very difficult to determine. The gauge on the dash seems virtually useless as it suggests the oil is way too low (in the red zone) until the car warms up AND is sitting at idle, at which point the needle points to the middle of the white range on the dial - which unintuitively means normal. I find the dipstick almost impossible to read. Sure wish there were a better and more precise way to measure the oil level.

randytrish

Sounds like the gage in the dash is working correctly. You should only be checking the oil fully warmed up and on level ground. It will take a while to get comfortable reading the dipstick. It actually helps when the oil is a little dark.
Randy

KeninBlaine

Yes, I know it is working correctly, I just find it unnerving to see it pointing to the red while driving. I guess as long as pressure and temp are good, there isn't anything to worry about.

Spokes

A 1/3 of a US quart ! OMG, I would get confused with that measurement system!

nine9six

Ken,
When checking the dipstick, it helps a great deal to put a clean paper towel on the dipstick, in order to visualize where the oil wicks off of the stick and onto the paper towel.

This method is especially helpful when the oil is clean and difficult to see the level.

KeninBlaine

Great. Thanks for the tip.

NP993

This is exactly how a dry sump lubrication system is supposed to work.

KeninBlaine

I understand that. It would almost be better for the gauge to be disabled other than the times when an oil level measurement is meaningful. But I'm getting used to it so no problem.

pp000830

Seeing what the cost is for a potentially unnecessary top end rebuild is, I believe this is probably the most valuable topic I have ever posted on Rennlist. I’m going out on a limb a bit, but I feel any road driven normally aspirated 993 (Carrera) that has been used exclusively for street driving and an occasional club auto-cross should not need any internal engine work beyond replacement valve lifter cartridges until well beyond 100K miles of use. The suggestion of such a need should always be suspect and the need validated by multiple persons via multiple diagnostic methods.
Keep those comments coming!

Andy

KeninBlaine

Yes, thanks for starting this thread.

When I purchased my C4S last month, there was a $6k receipt for a top end job about 10 years ago and at about 80k miles. When I read it closely, I noticed that there were new piston rings, but not any new valve guides - which surprised me. Seller told me it hasn't been using any oil, and it has been fine for the 6 weeks I've had it as far as I can tell so far. With 101k miles on it now, I'm hoping you're analysis is correct so I don't have to worry about another top end rebuild anytime soon.