Its a Mitsubishi. It burns oil like a furnace because Mitsubishi can't seem to build an engine that DOESN'T.
Seriously, its a common problem, and will not always be reflected with low compression or excessive emissions. There were 20+ TSBs written for "excessive oil consumption" for the Mitsu 3.0 used in Chrysler minivans, and all of them together don't completely solve the problem. Valve guides, valve stem seals, and the piston ring groove design all contribute.
George K wrote:
And furthermore, engines will consume excessive oil past the *rings* without loss of compression under certain conditions. The typical scenario is that the bottom-most ring (the oil scraper ring) is inadequate and leaves too much oil on the cylinder walls. Compression rings aren't made to scrape oil and will ride right over the film of oil, allowing it into the combustion chamber. They'll still develop full compression. Other possibilities are for oil to work between the compression rings and the piston and thus into the chamber, and this also can happen without loss of compression. Its due to a poor ring groove design more than to wear or an actual ring problem. Oil consumption past the rings was a long-overlooked part of the problem with the Mitsu 3.0 because the incredible leakage past the valve guides overshadowed it.
The oil consumtion problems with the Mitsu 3.0 used in the minivans was not seen on Mitsu vehicles. I think the marginal cooling systems and that poorly designed exhaust that wrapped around the cylinder heads caused most of the problems. It seems the heat buildup in the heads caused the valve guides to drop and most likely cook the valve seals. The same engine used in Mitsu vehicles did not have theese problems. The only known problem on Mitsu vehicles was lack of oil changes causing shortened valve seal life. If the oil was changed on time the valve seals would last till around 100,000 miles. I have never seen a Mitsu vehicle experience the dropped valve guides.
Yup, and the Chrysler version 3.0 used a different intake / injection setup than on Mitsus.
Anyway, the OP has a 2.4L. From the little I've seen, they seem like decent engines. Very simple, average power, reliable. This is from a small sample, mind you.
I would be looking at the PCV valve for a missing check ball if the OP is using THAT much oil out the exaust. Bad valve seals (assuming guides are OK as they probably are) shouldn't be able to leak that much oil.
Toyota MDT in MO
The dropped valve guide problem was a mechanical design problem, not anything to do with "marginal" cooling systems or "poorly designed" exhaust systems. If the engine had been under-cooled, it wouldn't have lasted as long as it did. Oil-burning and all, it was typically a VERY long-lived engine with a very reliable bottom end, which simply wouldn't have been the case if it were perpetually overheated. Furthermore, the problem was NOT unique to the minivan. All of the cars that used the
3.0, including things like the LeBaron that were far, far lighter than the minivans and therefore subjected to far less heat loading, had the same problems.The DOHC version of that engine used in the Mitsu 3000GT/Dodge Stealth never had the valve guide problem (because it had a completely different head design), but it DID always have the higher-than-typical oil consumption due to the piston/piston ring design on that engine. And in general, its much more common to see blue-smoking Mitsubishis than almost any other brand.
I have had the same experience with a very large sample.
If the valve seals are leaking it will use that much oil. I have seen this first hand many times.
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I have worked on both and I can tell you that the Mitsu's didn't have the dropped guide problem. It is just an educated guess on my part but the way the exhaust wrapped around the heads and exited out the back would keep alot of heat in the cylinder heads. I have had both chrysler and mitsu engines apart and the heads are the same.
If the engine had been under-cooled, it wouldn't have
I didn't say they overheated, I said they run hotter than in a Mitsu.
Oil-burning and all, it was typically a VERY
I agree. But i never saw a Chrysler car with the 3.0 have any problems it was always the vans.
Correct, but Mitsu also used the same SOHC 3.0 as used in the Chrysler vehicles. Only difference was the intake and fuel injecton.
but it DID always have the higher-than-typical oil
Never saw any oil consuption problems from any Mitsu engine due to pistons/rings.The only time we had any customer complaints on oil cosumption was the first few years Mitsu used the neon motor in the base model eclipse. According to Chrysler it was normal for an engine to use a quart of oil in
1000 miles.And in
Agreed. But is due to lack of oil changes more than anything else.
I am pretty sure that Mitsubishi changed the valve guide design in the later 3.0 engines, all the info I've run across on the problem only mention dropped guides being a problem in EARLY 3.0 engines.
Lack of timely oil changes leaves old oil in the engine, which carries a lot of stuff that can damage the valve seal material.
Ted
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