1994 850 manual Oil Loss.....No Visible Leaks

Post by **shaker_chi** » 16 Nov 2014, 18:17

I have an early 5 speed 1994 850 with 206,000 miles. For the past 6 months I am losing about a quart of oil every 1,000 miles driven. When I look underneath I don't see any leaks and I check my car every morning and don't see anything on my garage floor. Any suggestions?

Post by **abscate** » 17 Nov 2014, 04:49

That is slow enough loss that you might be burning it (rings, valve guides) without seeing any oil on the plugs or the exhaust. You can drive for a long time like this. Keep an eye on that oil though.

Post by **tryingbe** » 17 Nov 2014, 06:18

When was the PCV system last serviced?

Post by **phils94850** » 17 Nov 2014, 06:37

If you cant find an external leak then you need to do a wet/dry compression test to see the condition of your piston rings.

Post by **shaker_chi** » 17 Nov 2014, 15:45

A PCV was done at 200,00 and at 165,000 before that. It's 15 degrees in Chicago today, so as soon as I get a day over 30 I'll do a compression check. What should I expect from the compression test?

Post by **phils94850** » 17 Nov 2014, 17:48

Normal dry compression is around 140-170 I think

Post by **shaker_chi** » 29 Dec 2014, 10:24

Last time I check the oil I added STP oil treatment instead of the usual 5w30 and I have not lost any oil in the past 6 weeks. What effect does the STP have on the oil? Obviously, it will thicken it up, but how does this reduce my oil consumption? Just trying to understand the science behind it.

Post by **misha** » 29 Dec 2014, 17:28

It's simple.It makes the oil thicker,so it can't pass by the old valve stem seals anymore like it did before threatment.

You would have the same effect if you switch to higher viscosity oil....like 5w-40 or 10w-40.This "40"counts,because it is thicker at operating temperature than "30".