RX300 Excessive Oil consumption

I have a 2000 RX300. Purchased in Dec 2011 with 110K. Now, Dec 2014 with 170K. Over the past 20K or so, have noticed excessive oil consumption. I have tracked it for 6 months. Around town at lower RPM, it will go 1000-1500 miles before needing a quart. HOWEVER, at highway speeds (3000 RPM or higher; 70+ MPH) the consumption can be as high as 1 quart between fillips, roughly 200-250 miles! It’s not burning it out the tailpipe (no blue smoke) and it’s not leaking. Took it to a knowledgeable independent mechanic, with 7 years prior as a Lexus mechanic. Am being told it could be the valve covers because in 1996-2000ish 3.0 Lexus V6 (ES300 and RX300) the PCV is integrated into the valve covers and the baffles could be clogged. He believes there may be replacement valve covers that have larger baffles, and that replacing the valve covers may cure the problem. Any one else heard of this fix for excessive oil usage in the Lexus 3.0 V6??

If it was leaking that much out the valve covers, you’d think you’d notice oil dripping on the driveway when the car was parked, or at least the engine under the valve covers would be covered in fresh oil. One thing is clear, it has to be going somewhere. Possibilities are

  • leaking on hot engine or exhaust manifold, and evaporating off before leaking
  • leaking into coolant via head gasket breach
  • going out the tailpipe due to problematic rings, and not observed as blue smoke b/c the cat is burning it up first
  • going out the tailpipe, and not observed as blue smoke b/c the smoke only appears during start-up and not noticed as it happens briefly, due to leaky valve stem seals.

A couple of things that are easy to do, make sure the oil dipstick is firmly in place, and that the thing that covers the hole where you fill the engine w/ oil fits firmly.

My '96 Es300 didn’t have that problem in 150k. I’ve not heard of it (there are millions of 3.0 V6s out there), but if it is a problem, I would think a removal and thorough cleaning would fix the problem for, say, another 150k.

The Lexus forums have multiple discussios on the topic. There was an update to the valve covers.

The usual cause is sludge build-up on the cylinder heads under the valve covers. The sludge will prevent the oil from properly draining, this combined with old worn valve guide seals the engine can consume a lot of oil at high speeds.

I didn’t see any service bulletins for revised cylinder head (valve) covers.

I would have your front valve cover removed for inspection first. If there are signs of sludge/gel the fix is not cheap. If the engine looks good have both valve covers and the PCV replaced, it would also be a good time to consider having the valve seals replaced but that will add greatly to the repair cost.

Years ago Toyota/Lexus had a S.P.A. that addressed the oil gelling issue, but it has long since expired.

That guy on the forum had oil use problems starting around 150k+ miles. If it’s clogged baffles, then cleaning them should have been a reasonable solution, instead of replacing the valve cover. A new ‘old design’ cover would have fixed it too, right?

I’d stick a finger in the tailpipe and rub off a sample.

Maybe a dry and wet compression test would be in order to determine with at least a bit of certainty whether this could be related to piston rings.

It’s an aged vehicle getting up there miles and who knows how it was treated in the 10 years and 110k miles before you bought it.

I had a similar problem and fixed it by going up one weight in my engine oil. Most owner’s manuals will list 2 or 3 engine oil weight options. Why we usually choose to go with the lowest weight option is a mystery to me.

Thanks for all your input. ok4450 is right about maintenance in the first 110K miles - I don’t have any records from the prior owner - but the vehicle was close to spotless when I bought it, and the engine oil takes a long time to get darker between oil changes. I have put 10W30 or 5W30 (all Mobil 1) in it since I have had it, and of course change the oil and filter regularly (5K-7K miles). My mechanic is going to pull the front valve cover on Monday (12/29) to take a look.

Sludging should not be a problem with the Mobil 1…It’s a 15 year old car with 170K miles on it…More than likely, it will cost more to fix it than the car is worth…

Sometimes you can make a quick assessment the amount of sludge you’ll see when you pull the valve cover just by peeking inside the oil-fill hole with a small flashlight.

That same technique can be a good way to quickly verify the timing belt isn’t broken also, as you can often see the camshaft gears turning (or not) by looking in that hole.