High oil consumption

[clay1g]

My 87 911 has 81,000 miles and is burning between 1-2 quarts between fill ups. I've been using Valvoline 20W-30 oil and I'd like to see the consumption rate for 20W-50 before getting a top-end rebuild. Would I be wasting my time getting an oil change with 20W-50 or should I bite the bullet and get the top-end rebuild done?

[goat]

1 to 2 quarts between fill ups seems very high to me. Do you have leaks as well?
With that amount of usage of oil I can't imagine a big change between the 2 oils.

[Wil Ferch]

I'd like to hear more details...often, there is an appearance of high oil consumption when you fill to the "top" mark...we can go into that later only if it applies. Other times it looks that way if you have short drives vs long. Standing by...
--Wil Ferch

[clay1g]

My 911 leaks no oil and when I add oil, I add up to the middle of the dip stick markers.

[Wil Ferch]

Need to be real precise here:
When you fill, car is on level ground, engine is idling ( no too fast...say 800-900 rpm) *and* oil is up to operating temp..about 190 degF, say the 8 0'clock position on the gauge. Right?
If you then fill to mid mark, I would guess you really do have ( or are starting to have) high oil consumption.
--Wil

[clay1g]

When you fill, car is on level ground, engine is idling ( no too fast...say 800-900 rpm) *and* oil is up to operating temp..about 190 degF, say the 8 0'clock position on the gauge. Right?

Right. At this point, I know I have high oil consumption any way you slice it. I just want to know what kind of difference I'll have using 20W-50.

[Grady Clay]

WOW,

I’m impressed you can use that much oil and not be considered a mosquito eradication project.

Yes, fix the problem. Is it something like valve guides or rings? Do some through diagnosis before you start. Compression test, cylinder leak test, a high speed extended run on the highway.

To answer your specific question; yes, heavier oil will reduce the oil consumption – very slightly. You need to fix the root problem.

Best,
Grady

[Dan Owens]

Switching oil weights will do nothing to your consumption rate. You're losing oil somewhere either burning it or leaking it. How long has this been going on?

[stlrj]

Just curious, can you tell if your engine has been running a bit rich?

There was an observation by BA of a correlation between rich running DME engines and premature valve guide wear.

Cheers,

Joe

[Rot 911]

My '86 with 133,000 miles was consuming a quart of oil every 300-400 miles with no smoking! Turns out I had a burnt exhaust valve and all the exhaust valve guides were worn. All the oil was getting sucked into the exhaust unburned. I suspect at 71,000 miles you may be experiencing premature valve guide wear.