Watch closely when your car burns oil

Dear Tom and Ray: I have a 2001 Dodge Intrepid with about 110,000 miles. I have the oil changed regularly, but recently noticed smoke coming from my tailpipe when I take off from a stop. This doesn't happen all the time, but it's enough to make me nervous. I know the car has a lot of miles, but other than that, it runs well, doesn't make any funny noises and idles pretty quietly. I do have to add oil between oil changes. Should I be super worried? Any suggestions for what I can or should do without spending a lot of money?

Lisa

Ray: Well, I can tell you two things for certain, Lisa. First, you're burning oil. That's the smoke you see coming out of the tailpipe from time to time.

Tom: Second, it's not coming out from time to time, it's coming out every time you accelerate.

Ray: You may not notice it all the time because of the wind, or because you're -- get this -- paying attention to the road in front of you instead of looking for smoke in your rearview mirror. But I'm pretty sure it's blowing smoke all the time, because that's what cars do when they're burning enough oil to be visible.

Tom: What you do about it depends on how much oil you're burning. You say you're adding oil between oil changes. Are you adding a quart every 2,500 miles? In that case, you've probably got a long way to go before this becomes a crisis. The car could go for tens of thousands of miles. Or something else could end this car's life before your oil consumption ever does.

Ray: Right. Like a transmission failure. Or a run-in with a FedEx truck.

Tom: But if you're adding a quart every 300 miles, then you're already in a holding pattern circling the boneyard, and air-traffic control might clear you for landing there any time now.

Ray: In either case, you want to make sure you keep the crankcase full. Check the oil level frequently -- even more often than you think you need to -- because your oil consumption can increase suddenly, and you don't want to run out of the stuff. Plus, when the crankcase is full, the engine will burn less oil. That's because the lubricating work is spread among four or five quarts, instead of two, three or four. When there are fewer quarts, the oil has to work harder, which means it gets hotter and burns faster.

Tom: Also, keep changing the oil. A lot of people will say to us, "Well, I'm adding a fresh quart every week; why should I ever have to change the oil again?" The answer is, you can't decide which oil -- the old or the new -- the engine is going to burn. It's going to burn a mixture of new oil and old oil, leaving you with an engine full of the same mixture. So you still need to drain that old stuff out on a regular basis and refill it with new oil.

Ray: And you'll find that fresh, new oil burns more slowly than cruddy, old oil. So changing the oil frequently, and keeping it topped off, are two inexpensive things you can do to extend the life of the car.

Tom: But you've got an engine that's burning oil. And whatever stage it's at now, it's only going to get worse with time. So keep a close eye on it. And when you get to where you're adding a quart of oil every 300 miles or less, start looking at the '02 Intrepids. Good luck, Lisa!

Dear Tom and Ray: I'm a sales rep handling six states in the Midwest. I drive about 36,000 miles a year. I'm concerned about the amount of garbage cars spew. I'm thinking about finding a cleaner car, but the Toyota Prius and Honda Insight are not options. How can I find not only the most fuel-efficient vehicles, but the ones that also spew the least amount of pollution?

Christian

Tom: Well, generally speaking, they're one and the same, Christian. The less gasoline a vehicle uses, the less pollution it expels.

Ray: Right. There might be some small differences between cars that get the same mileage, because of specific engine technologies and different pollution-control systems. But broadly speaking, the better your mileage, the less you're polluting.

Tom: You say that the Prius and Insight are not options for you, but you don't say why. I'm guessing that you're either a big fella, or that when traveling 36,000 miles a year, you want something a little bigger and more comfortable in order to cut down on your chiropractic bills.

Ray: If that's the case, take a look at the Toyota Camry Hybrid or the new Nissan Altima Hybrid, both of which are pretty spacious cars that get about 40 mpg. Honda also makes the Accord Hybrid, but we don't recommend it because its mileage is mediocre.

Tom: If you're skipping the Prius and Insight because you'd rather buy American, unfortunately there are no large American-company hybrids on the market at the moment. But just make high mileage your top priority when you're shopping, Christian, and you'll be saving money and helping to save the planet. What a deal, huh?

Listen to "Car Talk" at 9 a.m. Saturdays and 5 p.m. Sundays on KRCU 90.9 FM -- Southeast Public Radio. Write to Tom and Ray at Car Talk Plaza, Box 3500 Harvard Square, Cambridge, Mass., 02238. Or e-mail them at the Car Talk section of cars.com.