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Disappearing oil

Dear Cartalk,

I own a 2000 Isuzu Rodeo. It has 110,000 miles on it. Although I wish the gas mileage was better, it runs great. It gets about 19MPG. It has a V6 motor. I have owned it for 14 mos. and have put on about 10,000 miles. Ever since I bought it I have noticed that it is frequently down on oil. I put a quart of oil into this thing about every 2 or 3 tanks full of gas. It never seems to have any color smoke coming out of the exhuast, even when accelerating, AND there is never any oil on the ground. Any guesses?



I don’t know how far you go on a thankful, but it would appear you are on the high side of oil usage. Many modern cars use what I would consider a lot of oil, but the manufacturers consider normal. Once the oil usage gets too high, it will damage the converter and you will get a CEL (Check Engine Light) or you will start seeing smoke out the tail pipe.

It is also possible at least part of the problem is the result of neglect or abuse by the prior owner. Not much you can do about that now.

Good Luck

If the engine is not leaking oil, which you say it isn’t, then the oil is being burned. There are no other options. The catalytic converter is very good at eliminating the oil smoke, at least until it gets clogged up.

We normally measure oil consumption in miles per quart. Without knowing how many gallons your fuel tank holds it’s difficult to calculate, but it seems your oil consumption is more than one quart per 1,000 miles. This is usually considered excessive.

I have a 1994 Rodeo and it has always consumed oil at what I consider an above average rate. My Isuzu mechanic seems to think that it is because of the different types of metal components which the engine is comprised of, which in turn react differently to temperature extremes during normal engine usage. Aluminum heads/pistons/etc… react differently to the steel block/components and therefore allow small amounts of oil into the combustion chamber which are burned and sent out the exhaust. He termed it “blow by”. Sounds logical to me but I sure would love to know if this is correct. The problem with this phenomenon is that the farthest point in the lubrication chain is often starved when the truck is low on oil and eventually components such as the lifter assembly will “varnish” over time and begin to stick. This has happened to me, so in addition to being diligent with checking the oil level regularly, when changin the oil I first drain approx. 2 quarts of old oil then add 2 quarts of transmission fluid to the crankcase, let the truck idle for 45 mins then drain immed. The tranny fluid is very acidic and helps to remove enough varnish to keep the lifters free… truck now has 233+k miles on it.

“A quart of oil every 2-3 tankful’s” tells us nothing. If it’s around a quart every 1000 miles, that’s fairly normal. What brand and grade of oil are you using?