Automania/Repair & Maintenance

Auto Questions And Answers For Week 31 Year 2001

by Bob Hagin

Q. My 1996 Ford Thunderbird has a 4.6-liter V8 engine. I've had it since new and it now has 90,000 miles on the odometer. It consumes about a quart of oil in every 1200 miles. There is no smoking that I can see. Is this normal? Where is the oil going?

A. There's only two ways that motor oil can get out of an engine once it's been put it. The first and most obvious way is through a leak from a faulty oil seal or gasket. This is easy to detect since it would leave oil drippings or spots under the car. If it was only leaking when the engine was running and/or when the car was underway, it would coat the underside of the car with oil and maybe even throw it up on the back window. The other escape path is out the tailpipe. For a variety of reasons, motor oil (and sometimes automatic transmission fluid) can be sucked into the engine's combustion chambers where it's ignited and sent half-burned into the exhaust system. On older vehicles, the half-burned oil comes out the tail pipe in the form of blue smoke. But since the '70s, most auto exhaust systems have been equipped with catalytic converters - muffler-like devices that become superheated in operation and more-or-less completely burns everything that goes through. Oil is burned to the point where there's no visible smoke. Eventually excessive oil going through the converter will "poison" it and then it requires replacement. I have Ford literature that states that oil consumption above 500 miles per quart is within factory limits.

Q. I would like to know about changing the motor oil and filter in a new car. They say that if you don't drive very much you should change it every 3000 miles or every three months. I take my car out of the garage once or twice a week and do all my errands. I put about 150 miles on it every month. Do you think I could go every 6000 miles or every six months? Would it hurt the engine?

A. Short errands around town are pretty hard on a new engine, more so than doing a lot of highway traveling. On short hops the engine most times doesn't get hot enough to get everything up to normal operating temperatures and boil off the water, acids and other oil contaminates formed by combustion. Oil contamination can lead to piston oil rings that gum up and stick. When this happens, oil can be sucked into combustion chambers and the vehicle becomes an oil burner. Your best bet is to base your short-hop maintenance on mileage rather than time. Since you probably won't be doing the oil and filter changes yourself, having the job done by a pro has the added advantage of getting the rest of the car checked for excessive tire and brake wear, muffler rust-out (a common problem with short-hop cars) and other out-of-sight potential problems.

Q. About two years ago, I bought a 1990 Suzuki Sidekick SUV in order to have a four-wheel drive car to use when I go fishing in remote areas. It was relatively cheap and seemed to run fine. Now my son has a driver's license and wants to drive it to high school. It has always had a squeak in the rear brakes which I was willing to live with but now that my son will be using it, I'm somewhat worried about it. I had the rear brakes inspected but the mechanic said that they looked fine. Could the noise come from a bearing that could lead to trouble if it's used every day?

A. I came across an old Suzuki service bulletin that says a squeak in the rear brakes of a Sidekick may by caused by the lining on the brake shoes being too hard. This hard lining has been know to "craze" or score the rear drums so when shoes with a softer material are installed, the rear drums may need to be remachined back into shape or replaced.