Toyota 1MZ-FE burning lots of oil

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A family member has got a 2002 Toyota highlander with the 3.0 V6. When I saw it last I noticed it was low on oil, like real low, not even on the dipstick. At this point she was about 6 months and 4000km into her last oil change. She religiously follows the oil change sticker, and was about to get one anyways, so I offered to do it for her. I drained just over a liter of oil out of her pan, the car takes about 5. What could be causing such high consumption? The car has 250k km. Doesn't really smoke. Looks very dry from underneath and is not leaking. I checked the pcv valve and it seems to be operating properly. She has receipts from the previous owner, so I know that the engine was well maintained. Oil changes were done on time, and all but three were done at a Toyota dealership (including the one I did). The dealer has never told her that they barely got any oil out of it. I know this engine has a history of sludging, but given the service history, I imagine that wouldn't be a problem. However, isn't unlikely if the engine is running on small quantities of oil. Anybody familiar with the engine have any recommendations on what we should do? Would It be a good idea to start running a high mileage synthetic? I put in some Motomaster 5w30, in case anyone is wondering.
 
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The local dealer is pretty large operation and has one of the express drive through oil changes. I do believe they change it, if anything they may have under filled. I'd like to give them the benefit of the doubt. I did change the oil and will be monitoring the situation, but assuming the worst.
 
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The 1MZ is one of those engines where a 3k OCI on synthetic is a good idea, anyway crzy Does the car leak any oil? Valve cover gaskets can go bad over time, and they are impossible to replace in the 1MZ, and you can't see anything under the oil cap because they put a baffle there mad
Originally Posted by Ded Mazai
Stuck/worn piston rings. I doubt you can do anything about it. Oils or oil system flushes are useless in this case.
If that is the case, an Italian tuneup might work drive ontome
 
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How about a piston soak with Kreen or Berymans B12 to maybe loosen the piston ring crud. Do this right before an oil change. Some toyota engines on the mid 2000s had anew piston design that was prone to piston slap and eventually burning oil. The supposing part was no oil light when it was that low. My niece has a Sion that was burning so much oil that the oil light would come on at about 1500 miles. She didn't know any better and just brought it into the dealership. They "changed" her oil (4qts of dino) and aired up the tires for $40 and sent her on her way. That's when I taught her to buy some cheap oil (super tech or Chevron) and keep in the trunk. Every fillup check the oil and add a little bit if it is low. She got scared when she went the actual 5000 miles on the OCI and the maintenance required light came on because she never saw it before. smile She was always seeing the oil can light thinking it was telling her it needed an oil change when it was really just low.
 
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Id change the PCV valve out anyways. Its under 10$. But id highly suspect a bigger issue as others have mentionned. Id give it some HM oil and a new PCV and check on it in 1000km. Show her how to check and add oil...seems to be a lost art.
 
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Those 3.0's were oil drinkers. I believe low tension rings and/or undersized oil drain holes (which get clogged up if run on long OCI with conventional). I'd check the oil more often and just keep topping off. Show her how to do it on a cold engine, like every Saturday or Sunday morning. Just pull the dipstick and check. Pretty easy to add oil! Do check the manual, i'm not sure if the bottom of range is a quart or not (but just dumping in a quart when it shows low is probably just fine, a bit over won't hurt anything).
 
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4,616
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Fort Worth, Texas
The 1MZ-FE engines I've been around never used much oil, Now they will definitely start leaking it! Cam seals & Valve Cover Gaskets being pretty common. The drain back cavities are huge. Even the heavily sludged ones seem to drain quite well. I don't believe the MZ used low tension rings or had ring pack issues? The Valve Covers can get clogged up (between the baffle & cover).....Around 2002-2003 is when the covers were redesigned, The easiest way to tell you have the update is the Screw-in PCV valve.
 
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