engine using too much oil

[Craig]

I have an 89 sho (since 1990) with 142,000 easy driven miles on it. The car is in good shape and runs well.
There is no oil on my garage floor, no oil smell when I pull into the garage after a drive, no smoke when I'm driving, pretty much keep to the low RPMs, and the mechanic sees nothing. And again, the car runs well and has been pretty well maintained. But the car is using a quart about every 400 miles. I'm thinking it should be more like 1 every 900 miles or so. Would anyone care to speculate about what can cause this kind of oil use. I'm thinking I should be seeing or smelling something. But I'm not.

 

[sholxgt]

What weight and type of oil are you running?

Neither of my sho's used more than a quart every 3,000 miles, but I did run thickish oil in both of them. I'm sure it's not recommended now, but I ran 20w50 Castrol in my '89 and 15w50 Mobil 1 in my '93.

As far as your usage, it's hard to say. Those motors like to leak oil around the valve cover seals and into the spark plug holes. I'd check there for oil contamination. With the age, you might also be getting oil passing the rings and burning off.

One thing I'd advise is to run it harder also. Both of mine saw redline daily and went over 230,000 miles with minimal problems. IMHO, those motors do better when run hard.

 

[rubydist]

These motors when driven "easy" will get sticky rings and will use too much oil.

BTW, I have had SHOs with exhaust valve seals completely gone and still used less than a quart in 1000 miles. Because of how the valve shim keeper drops down over the stem of the valve, not much opportunity for excess oil consumption with bad valve stem seals.

I have had excellent luck using Motorcraft semi-synthetic 5W30 to free up sticky rings. Just run that for a couple oil changes and I think you'll see a big difference. And I agree with sholxgt that you need to run it hard once in a while - just make sure the oil is completely warmed up before you start mashing on it.

 

[sholxgt]

These motors when driven "easy" will get sticky rings and will use too much oil.

just make sure the oil is completely warmed up before you start mashing on it.

x2 on the warm up. They are old school motors that do best when treated as such. They like warm oil, cold air, and a heavy foot.

 

[sperold]

My 89 used a lot of oil when I used fully synthetic oil.
When I went back to regular oil, and went with more viscosity, the consumption went down.

It is the first car than I ever saw the low engine oil light come on. And often it was not long after an oil change.

But I had way over 200K miles, but like you, I never saw any smoke or had any drips.

Can't explain it.

 

[zak]

Also check that the PCV system is free of varnish/obstructions, this will improve ring seal. There is some sort of separator (oil/air) that bolts into the top of the block below the intake, it is not often that you hear about folks cleaning these on SHOs, but you do on other engines (the ports in the throttlebody are also key areas). While I like rubydist's Motorcraft semisynthetic idea better, have also used AutoRX on one SHO engine in the past to try to free up rings.

 

[Craig]

Thanks for the replies. I have been using 10w30 for awhile. I'll try your suggestion. And your point about driving it a little harder is well taken. I appreciate the help.