My '93 with 343K miles suddenly seems to be using a lot of oil, like 300 miles to a quart. This is down from about 2,000 miles to a quart. The strange thing is she don't smoke, she has full power, and apparently fine compression because she can sit a week and start instantly. I have no idea what's going on and hope somebody has experienced and solved this one!
Thanks for reading!

George

 

Blow-by or a leaky seal?

Check your turbo as well and make sure it's not pushing oil down the intake. I had an engine once that started clean and ran clean but one day when I took my intercooler off I noticed a bunch of oil that came from the turbo..

 

Thanks, I'll have that done. This oil use happened very suddenly! I had towed our 8k pound 5th wheel up into the Canadian mountains and checked the oil one morning. Wow. It took 2 gallons to fill it again. Running that low didn't seem to hurt it but sure made me feel bad.
No, there's no sign of blow by (at least bbad blow by) and she doesn't seem to leak, although there is some spots on the ground when parked. But the engine block stays clean so it isn't as dirty as it was when we had the main seal replaced at abuout 250K when the transmission was replaced.
Appreciate the comment, thanks again!

George

 

My old 91 would go through oil when towing heavy, but return to normal afterwords. Towing, it was hard to tell if it was coming out the exhaust or not due to normal exhaust output under load. I suspect it was blow by from hot oil vapor off the bottom of the pistons.

 

Thanks. I think next time I change the oil I'll send a sample off for an analysis to see what if any trace metals show up, which hopefully will tell me what's happening inside the engine.

George

 

Oil analysis is only useful if you have other samples to compare against, we do this in aviation. If you are concerned about it, cut your oil filter open and pull out the element. There will always be some ferrous and non-ferrous particles in it.

 

So, you would consider a random single sample with alarmingly high levels of say fuel or chromium for example, useless?

 

I would guess a bad/worn turbo seal... either pushing oil into the intake or out the exhaust. Most likely the intake if you aren't seeing smoke, because its being properly burned. Open up your intercooler piping and check.

FWIW, I put a couple gallons of filtered WMO in with every tank, and I actually get less smoke.

 

I make no claim on being a mechanic however..... Oil analysis if done regularly, like many fleet companies do, will show wear progression. But, it can also be a diagnostic tool because it tells what traces of what metals are in the oil, and can predict wear inside the engine, I hear. Cutting open the oil filter will show particles of steel if things inside the engine are really going to pot, l but the oil analysis will show internal wear. I learned this when selling an old diesel Benz. The guy came, took oil samples from the engine, tranny, and rear end. I knew the car was tired but the report came back saying it was shot. The price dropped accordingly. Oh, there's no hiding either. Changing the oil won't hide things once the engine has been started and warmed up just once.

 

Oil samples have saved my engines more than once - not depending on any so-called "trending" data either. The 1st Gen showed high silicon the very first time I sampled it because the nit-noid PO was running a K&N filter on it. Guess what? Oil, oil filter and air filter all got changed right away. Wife's BMW 335D showed 4% fuel with a clogging/dirty air filter. And no, it had only been run about 10k miles, well ahead of scheduled replacement. Guess what? Four quarts swapped out, filter got changed, Filter Minder installed and engine's still running strong. Either one of these cases would have certainly led to premature engine failure from excessive wear without early warning from oil analysis.

Oil analysis is a valuable tool in many different possible maintenance scenarios and failure modes in the the toolbox of somebody who knows how to use it.