Q–I have a ’91 Cadillac Fleetwood Brougham. The owner’s manual allows 7,600 miles on the oil. If I do a couple four-mile trips per day, will one 70-mile trip on the highway each week clear up the oil until I reach the 7,600-mile total? C.G., Chicago
A–We don’t have a slick answer for you. While most of your daily driving falls into the “severe” category, that weekly trip will cook off the accumulated moisture in your oil.
That said, we still think you should follow the schedule for more frequent oil changes.
They are an economical insurance against costly engine problems. Look at it this way: Three thousand miles to a gallon (of oil) ain’t bad.
Q–My 1996 Volvo is black, and I am wondering why there are so many very fine scratches in the paint that you can only see in direct sunlight or under fluorescent lights. Can you recommend something for me to use that will help take care of this problem? I would love to see my paint as showroom new again. M.D., Bartlett
A–We love a shiny black car but would never own one (though our wife does). They only look good when they are freshly washed and waxed but that usually lasts about 10 minutes or 10 miles, whichever comes first.
The scratches you see are in the clear coat of your car’s finish, and there are some excellent professional glazes you can use to polish them out. The products often sell for $10 to $15 per quart.
Just be careful not to be too aggressive. Once you have polished out the scratches, give your Volvo a good wax job. Then, clean and wax it often.
Q–I agree with your response to R.E. in Des Plaines (Motormouth, Aug. 31) that today’s cars have great transmissions and low-friction bearings and coast easily.
I am sure that R.E.’s Eldorado has a four-speed automatic, as does my ’96 Z-24. Is it OK to downshift into third gear to help slow the car and put less wear and tear on the brakes? Or does that downshifting put more wear and tear on the tranny? P.V., Downers Grove
A–Let’s look at this problem scientifically. To slow a car, you must convert its kinetic energy into another form of energy. In the case of the brakes or transmission, it becomes heat energy, and that’s what causes wear and tear.
Now, let’s look at this question from an economic standpoint. Which system is cheaper to overhaul? If you said the brakes, you’re right.
Q–I own a ’91 Ford Taurus with four-wheel disc brakes. In April 1996, I had new calipers and pads replaced. About two months later, I started to hear a grinding sound coming from the right rear. It would start after driving about 10 minutes.
Three times I took the car back and, as you would expect, each time there was no grinding noise. One time I left it overnight and they had it for the entire day. They said they never heard the noise. They have given great service but cannot solve my problem.
Does this “sound” like a warped rotor that goes in and out depending on the heat? Could they have overtightened the lug nuts and caused this intermittent problem? C.S., Buffalo Grove
A–A warped rotor is something that you usually feel, not hear. It will cause a vibration when you apply the brakes.
Grinding and squealing noises are usually the result of a brake pad, or pads, vibrating the caliper. Usually anti-squeal compound or shims will stop the noise.
Q–I have a 1994 Plymouth Grand Voyager with the 3.3-liter engine that is difficult to start hot or cold. I have had it to the dealer twice, and the problem still occurs. Once they replaced the oxygen sensor, which seemed to help a little. The second time they cleaned the throttle body, which was no help. Any ideas? B.K., Chicago
A–The oxygen sensor has no effect on your engine until it warms up, so it cannot contribute to the starting problem. We have a hunch it may be related to the fuel system.
A recalcitrant fuel pump relay may not be sending power to the pump when you first turn the key. Or, a faulty fuel pressure regulator may be allowing the system to drain down, which results in long cranking times before the engine starts.
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Bob Weber is a Virginia-based free-lance writer and former editor of an automotive trade magazine. He is an ASE-certified Master Automobile Technician, having recertified every five years since 1978, and has worked in service stations and independent repair and specialty shops. Address your technical questions about cars and trucks to him in care of Motormouth, 17717 Silcott Springs Rd., Purcellville, Va., 20132. Send e-mail, including name and town, to motormth1@aol.com. Answers will be supplied only through the newspaper.
