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I think my friends Lexus RX300 is burning oil. What causes it, what is it technically doing and what fixes it?
 

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Not a direct answer, but a thought... If ANY car is not burining oil there is something wrong... It's one of the major reasons youhave to change it... The amount you put in is never the same as the amount that comes out...
 

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Miroudias said:
Not a direct answer, but a thought... If ANY car is not burining oil there is something wrong... It's one of the major reasons youhave to change it... The amount you put in is never the same as the amount that comes out...
Well, yes and no. Some engines use more oil than others. Some seem to hardly use any. Some have an "acceptable" amount of usage, like DC says that one quart every 3000 miles is acceptable. I think somebody said once that 1qt per 1000 miles is acceptable per DC but that seems very eccessive.

Well, when a car is burning oil, there's a number of things that can be wrong. It could be one or a combination of things. Obviously the amount of mileage on the motor will be a big contributing factor. Probably the most major and common culprit of burning oil is worn piston rings and cylinder walls. As the engine ages, the rings don't seal as well to the cylinder walls and it allows oil into the cylinders and, you guessed it, gets burned. Another culprit is leaky valve guides/seals. Any oil sitting on the top of the cylinder head will drain down past the valves when the guides/seals or even the stems of the valves themselves are worn. Chevy engines are notorious for exhaust valve guide issues. They have a trademark "blue puff" when first starting after its been sitting for awhile. Another possibility is a leaking head gasket. Not only does the head gasket seal the cylinders from the water passages, but also from the oil passages. And another possibility is a malfunctioning pcv system. The pcv system purges crankcase vapors into the intake manifold to be re-burned. When things aren't working correctly (like a plugged up pcv valve) then oil can find its way thru the breather and into the intake. And those crankcase vapors come from blowby past the piston rings. So when there is piston ring/cylinder wall issues, there will be more flowing thru the pcv system.
 

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froggy81500 said:
Well, yes and no. Some engines use more oil than others. Some seem to hardly use any. Some have an "acceptable" amount of usage, like DC says that one quart every 3000 miles is acceptable. I think somebody said once that 1qt per 1000 miles is acceptable per DC but that seems very eccessive.

My galfriend's 92 Caravan 3.3 has always used oil, and the Dodge dealer was willing to do a rebuild if it used more than a qt/900 miles. Of course it used a qt/1000 miles. Ford considers anything down to 500 miles/qt normal.
 

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WOW! 1 quart per 500 miles! No wonder why the oil companies are hitting the jackpot. Sorry, but if an engine is using that much oil, its time to put it out to pasture. Not to mention the added pollution is causes by burning that much oil.
 

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The caddy North star V-8's use a qt every 500 miles or so. And its normal, no wounder they hold 7 1/2 qts of oil. My wifes 50,000 mile PT use's a qt every 3,000 miles. The 98 Stratus we traded in on it. Had the same 2.4 DOHC 4 banger in it. And with 99,000+ miles on it. It only used maybe a 1/4 of a qt of oil in 3,000 miles.
 

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I've only owned 7 cars in my life. All of them burned less than 1qt in 3,000 miles. All of them were mopars. My first car was a '72 318 powered Duster, sold with 154,000 miles on it and still used less than 1qt/3,000 miles.The '94 3.3 trep in my sig used less than 1qt/3000 miles. When I bought my '03 SXT, the dealer changed the oil,when I first brought it home the oil was at the full mark, 3,000 miles later , I checked it b/4 I drained it for oil change. It was still at the full mark. If DC says 1qt/1000 and Ford says 1qt/500 is normal, then I say they are full of crap. A Lexus is supposedly a high quality car, if it's burning oil excessively, it was probably maintenance neglected maybe by a previous owner. Way too many people believe Jap and Euro cars can run trouble free without all that maintenance that our crappy domestics need.
 

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go onto bobistheoilguy site and look up toyota sludge-you'll learn all about these 3.0 v6 motors and probably an answer.
 

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A Lexus is an expensive Toyota. But besides that, if an engine is not broken in properly (like raced around fresho ff the lot) then the rings and cylinders don't seal as well. So right from the get go, it'll have a higher rate of oil consumption. I've owned 15 vehicles (including the ones my wife and I own or owned jointly). I've had some, like the 1980 and 1981 Chevettes, that pretty much had the same amount of oil at oil change from the previous oil change. then there's some of the Fords I've owned that burned oil and leaked oil. One with a bad rear main that went thru 4 to 6 quarts a day, depending on how much I drove! With my trep, I've kept a closer eye on it. I've noticed typically around 1 quart give or take a few ounces between oil changes (average 3500 miles). But, depending on what brand and weight oil, I've seen it use it quicker. Like for one oil change last summer, I used 10W-30 instead of 5W-30 like I normally do. I had to top it off a couple times before changing the oil, about 1 1/2 quarts or so. One thing I have noticed on this motor and the 2.4L in my old '98 caravan, is a decent amount of oil going thru the pcv. On that caravan, I temporarily replaced the pcv hose with clear tubing until I got emisions hose. That tubing turned amber in about a week and with the engine idling, I could watch the beads of oil getting pulled up thru the hose. On my trep, I've got oil in both the pcv hose and the breather hose. No, I don't have issues with my pcv system, the valve was replaced last year. I've read that DC didn't properly baffle the valve covers. I dunno, but it would make sense why there'd be oil in the breather and pcv hoses and some oil consumption. Here and there someone comes along making a oil catch can out of an air compressor filter. Not a bad idea, eventually I might get around to trying it and seeing if it impacts my consumption. but 1 quart at around 3000 miles doesn't seem too excessive to me.
 

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I've owned over 50 cars/trucks. This 94 3.5L has the lowest oil consumption I've ever witnessed. My wife mostly short trips city drives with it and it's never less than 1/2 way between add and full after it's 5000km oil change interval.

We once drove it round trip from Ontario to Florida. After 4000km the oil was still at full and clean too.

I have a 95 Thunderbird LX with a 4.6L that needs valve seals. It's drinking the oil at a rate of 1L per 1000km.

You can usually recognize oil consumption by when you see the smoke.
After extended idling, valve seal.
During full throttle. rings and or cylinder walls.
 

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jfsram said:
You can usually recognize oil consumption by when you see the smoke.
After extended idling, valve seal.
During full throttle. rings and or cylinder walls.
Not always. If the consumption is not that bad, you might not ever see smoke. I once saw an S-10 in the village near me that smoked up the entire street, kinda like the smoke you'd see running seafoam! the cops pulled him over and had the truck towed. And it was oil, could smell it along with the grayish blue color.
 

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froggy81500 said:
Not always. If the consumption is not that bad, you might not ever see smoke. I once saw an S-10 in the village near me that smoked up the entire street, kinda like the smoke you'd see running seafoam! the cops pulled him over and had the truck towed. And it was oil, could smell it along with the grayish blue color.

So what are you trying to say?
 

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jfsram said:
So what are you trying to say?
Exactly what I said. If the oil consumption isn't that much, then you won't see any smoke. My engine uses about a quart between oil changes. Where's it going? Obviously its burning it, some probably past the rings and some thru the pcv system. So there is oil burning going on in my engine, yet there's no blue smoke to show for it.

In the case of the chevy pickup i used to have, the valve guide seals were worn, so when it sat overnite, the oil on the heads would leak down into the cylinders. I'd get the trademark "Chevy blue puff" when I first started it every morning. But that's the only time I'd see any oil smoke out of it. I can guarantee oil was leaking down when it was running, but not enough to show any smoke. Not until there was enough oil leaked down from sitting, did it smoke.

So what I was saying before, and again, is that the oil burning can be so minor that there won't be any smoke from it. Obviously, if you do see bluish/grey smoke, then its starting to get significant.
 

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Yes I agree. The comsumption would have to be significant if you are burning enough of it to see it.

And yes 1 quart / oil change is NOT my idea of significant but normal.
 
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