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Where is my oil going?

My 95 Honda Odyssey has 200,000 miles on it. It has the original engine, so it’s understandable that it would leak oil. It’s never had a ring job but the engine gaskets were replaced a couple years ago. Also a new oil pan and gasket were installed about a year ago after the old pan got dented on a curb. It had been using about a quart of oil every two weeks and these repairs did not fix this.
What puzzles me is where the oil is going. It never leaves drips on the driveway and also doesn’t smoke, at least not that I can see. There is a slightly hot smell when I shut it off, but no visible smoke. Somehow a lot of oil is leaving the engine, but how? Where is is all going?

Badly-worn piston rings would result in oil consumption (burning), but would not cause external leaks.
As to no visible smoke in the exhaust stream, your catalytic converter will “consume” oil that is getting past badly worn piston rings…up to a certain point…and that situation will eventually lead to failure of the very expensive catalytic converter.

If there are no external leaks, then the only two possibilities (IMHO) are internal consumption of the oil as a result of worn piston rings, or a breached head gasket. When you last checked the oil, did it look “normal”, or did it look like a chocolate milkshake?

Ultimately, the answer to your question is “Into the air.” Sounds like it is getting past an oil ring or rings and becoming part of the combustion process. I checked CarComplaints to see if this is common to this model, but it is not. There was a TSB on an oil seal for that MY Odyssey, but it was almost two decades ago and you would have seen the leak.

After 200k miles, I think it is reasonable to assume that there is sufficient wear on the piston rings to result in some oil consumption. Exactly how much oil is being consumed is most likely a function of the type of maintenance that the engine received over the past 22 years.

The OP needs to learn about oil leaks, vs oil consumption with engines that have been in service for more than 2 decades.

I agree and disagree. If oil is being used then it’s either leaking externally and should be visible or it’s being consumed internally in the combustion chambers or catalytic converter(s).

However, oil doesn’t have to look like a milkshake for this to happen. That would indicate a coolant leak. If coolant consumption is not an issue, it is quite possible that the consumption can be attributed to worn rings or a head gasket that is leaking oil into the combustion chambers (and not coolant) and the oil looks like oil.
CSA

My thought is your spark plug condition or a pressure test would be needed to put the rings as a suspect. It may be oil is getting blown away. I have 188k and no oil burning or loss so negligible I have never even been down 1/8 of a quart, so If you have done regular maintenance your piston rings might be ok. From this site I have learned a bad pcv valve can cause oil consumption with many other possibilities. A good mechanic should be able to tell you what is going on.

Out your tailpipe. Think of how many hundreds of thousands of revolutions that engine makesevery day. Even if it used less than a drop of oil every hundred revolutions, that would add up to a lot of oil being lost. How often are oil changes done? Might be time for a $25 oil analysis to determine wear particles in the oil.

The OP already stated that there are no external leaks. Neither of us are there to confirm that assertion, but if we assume that it is accurate, then this has to be a case of badly worn piston rings–which certainly shouldn’t be too surprising with a 22 year old engine, or–possibly–a breached head gasket.

Wow. We’re all 100% in agreement. How often does THAT happen! :stuck_out_tongue_winking_eye:

Sounds to me too like you’re burnin’ oil. Sounds like the engine is worn out and tired.
I am too, but I make gas instead of burning oil.

A wet & dry compression test should be revealing. Give it a try and post the results.

1 Like

Purchase a can of RESTORE and add it to the engine oil.

https://www.restoreusa.com/index.php

If the oil consumption slows down or stops, the problem is with the piston rings.

Tester

Concur w/TSB’s idea for a wet & dry compression test. Meanwhile, good idea to frequently monitor the oil and coolant appearance & levels until this is resolved, just in case the oil is escaping into the coolant. Take a look at the inside end of the tailpipe too. Compare it to your other cars, or friend’s cars. Is yours noticeably more black and greasy inside the tailpipe? Or does it seem to be about the same as other cars? One more idea, have someone watch the tailpipe when you start the engine first thing in the morning, or when it hasn’t been driven for 4 or 5 hours. Is there a brief cloud of smoke that quickly goes away? If so the problem could be caused by faulty valve stem seals. If you have to have a serious engine problem, that’s the best one to have of the ones mentioned above. That can be fixed without disassembling the engine usually.

I still advocate a compression test, but you could also follow up with a can of Restore. I doubt that it’ll help more than maybe once, but hey, the engine’s worn out anyway. Whatcha got ta lose? Let us all know how you make out.

Additives can’t fix wear. But it MIGHT buy you some time.

Yes compression tests are the way to go, but brought my boat motor back to live once with a Yamaha ring decarbonizer cleaner whatever, koched up rings or something.

Thanks for all the replies - what a great community this is! I will try compression testing and a can of Restore. Thinking of how slowly the oil could be burning off explains the lack of smoke. At this point the whole thing is more a matter of curiosity. As my mechanic said, “You rode this horse a long way. It’s time for a change.” I do have another car, I’ve gotten my money’s worth out of the Odyssey, and I’m looking into giving it away to somebody who needs a free vehicle. I just want them to know what they’re getting. Again, thanks for the replies!

Assuming your mileage has been consistent, that is a quart of oil every 300-400 miles. That is a lot.

On the other hand, 2 quarts of oil per month is about $6. You could continue in this mode for years.

That is true, but I doubt if he would be able to drive for two more years without replacing the catalytic converter. All of the oil smoke that the cat is “eating” will take an expensive toll on the cat long before he can get to the 2 year mark.

good point.

Back before it finally bit the dust, my diesel Olds was using a quart every 500 miles. There was no smoke or other evidence out the tail pipe.

My 1986 ford Tempo (bought new) used a quart of oil every 600 to 1000 miles the entire 130,000 miles I drove it. Never a cat problem.

Years ago my 1984 Chevrolet Cavalier 2.0 L engine was starting to use oil. I started adding the recommended amount of Marvel Mystery Oil to the gasoline, and the oil consumption went down significantly. It is supposed to free up stuck piston rings, and maybe that’s what it did.