5 Quarts 1500 miles?

[El_Mecanico]

I don't get it, I changed my oil 1500 miles ago and when I went to change it from 0w40 to 15w50 Mobile 1 yesterday I only got maybe 5 quarts total out of the engine and tank. I also conducted a compression test and had between 80-90 PSI. The engine runs fine and spark plugs are clean with no trace of oil. The engine doesn't leak or burn oil. I'm really puzzled now. Also when I pull one plug wire at a time there is very little engine change noticeable is this normal? Do you think the engine was damage with only 7-8 qts of oil remaining. The engine oil light never turned on and there is no noise present. Would it be possible the compression tester gage is wrong? I did check the engine cold and did not open the throttle all the way. Do synthetic oils smoke when burn? Anyone have any ideas? Thanks.

[El_Mecanico]

Compression test was done while engine was cold. Also I added 11 qts of oil about 1/2 inch short from full on the dip stick.

[EarlyPorsche]

If I am not mistaken you are supposed to take compression tests with all plugs out and wide open throttle. Someone else will have to confirm this though. I can say that on a dry sump system if you had oil in the tank it was probably pumping but with higher temperatures and it could have cavitated a bit with less oil. Try and keep an eye on it more this time.

[Wayne 962]

Compression check does have to be at wide open throttle, but removing all of the plugs is optional (although you have to take them all out anyways, so you might as well and give the starter an easier job). As for measuring oil loss, I don't think you can get an accurate reading here. You need to fill the car up, measure the dipstick, drive 500 miles and then remeasure. In this case, you are measuring two different things, which may be affected by other factors.

-Wayne

[Por_sha911]

Lets start with some basic questions. Did you check the oil with the engine warmed up, running at idle on level ground?

[El_Mecanico]

I will find another compression tester and redo with all plugs out, full throttle, with engine warm. Oil tank was checked while idling, engine hot and car level. I wonder if 0w40 should be used on these older Porsche model (air cooled) that is? Thanks for the feedback. Will provide info follow up.

[El_Mecanico]

Amazing when you open to full throttle and engine hot. Here is the results.

1. 181
2. 182
3. 182
4. 179
5. 182
6. 181

Close call I was ready to sell the car.

Next step why does the engine surge as I accelerate? Do I need an O2 sensor?

[Zeke]

I don't think 0-40w synthetic is a good idea on the older air cooled cars.

The oil system will work with a lot less oil than full, but the cooling effect of the oil will be compromised.

[rfuerst911sc]

I would think for your climate 15w40 or 20w50 should be used.