Western-Star

Q Recently I read an article that said Ford Motor Co. has raised oil change intervals from 5,000 to 7,500 miles due to new engine designs. In the same article, a representative from General Motors said that engine oil might last 12,000 miles.

I read your column and you always suggest changing the oil and filter every 3,000 miles. Should I change my oil and filter change habits for my 2000 Mercury Sable and 2002 Buick LeSabre? J.B., St. Paul, Minn.

A Thanks for sending a copy of the article.

It does say that modern oil is more robust than it was 15 years ago. It also says that oil can lose its lubricating properties in extreme cold and heat. I agree that modern engine oil, indeed, is more resistant to thermal breakdown than it was 15 years ago.

You also might have noticed that the spokespersons for the various companies never mentioned what happens to the dirt and grit the oil accumulates as you travel along. Does it disappear? Does the oil digest it and turn it into substances that aren't harmful to the engine? The answer is no.

As you drive, particles of dirt, sand, carbon and everything else that floats in the air ends up in the engine oil. Also, fuel and moisture accumulate in the oil. This combination of material is abrasive and causes every moving part in the engine to wear. The more miles you leave oil in the engine, the more material accumulates in the oil to wear bearings, piston rings and such.

Also, let's not forget that once the additives in the oil break down, sludge and varnish develop in the engine.

You also might consider that automakers are in the business of selling cars.

The longer a motorist keeps a vehicle, the fewer new vehicles are likely to be sold by the carmaker. You might consider keeping a car longer if wear hasn't wreaked havoc in the engine or transmission.

You might have also noticed in the article that the spokespersons are suggesting how convenient it is not to have the oil changed as frequently.

I don't know of too many people who like to take time out of a busy schedule to have the oil changed, but it is one of the most important steps you can do to prevent wear.

I see the effects of what happens to engines on the extended oil change interval plan, and it's not pretty. Since this is the case, I continue to suggest oil and filter change intervals at 3,000 miles. Consider your oil change intervals carefully before you make a decision.

Parts don't last forever

Q The power door lock in the driver's door of my 1999 Ford pickup quit working right after the factory warranty expired. I replaced it and it works fine. Now the power door lock in the passenger door quit working and I refuse to replace it. W.B., St. Paul, Minn.

A It would be nice if we could purchase a machine and never have to replace a part. Vehicle designers and engineers build a vehicle within a budget. As a result, parts are used that are not perfect or meant to last forever or for that matter, the life of the vehicle that isn't built to last forever. As a result, parts break and wear out.

In your case, the door lock actuator electrical windings probably failed. To fix the trouble, replacement of the faulty part probably is the cure.

There Is Hope

Q The voltage in my turbo-charged 1989 Audi Quattro intermittently goes into a discharge mode. The battery has been checked and found to be fine. The alternator was replaced with a rebuilt unit and passes tests.

When the voltage goes into this discharge mode the voltage is 12 volts. I know that it should be more. Also, when this occurs the anti-lock brake light illuminates and the system does not work.

I can counter this problem by turning off the engine. If I immediately restart the engine the charging system returns to normal voltage and everything works fine. However, sometimes when I do this the engine cranks but won't start.

I love my car but I'm thinking I should give it up. What should I do?

S.W.S., Coon Valley, Wis.

A I know that sometimes it's difficult to give up a car. Don't give up just yet. It's possible that the trouble is caused by corrosion. Check the battery cables for corrosion that may have infiltrated the cable strands.

Also, check the cable connections especially the ground connection on the engine or frame for corrosion and security.

If corrosion has infiltrated the cables replace them. If a poor connection is at fault make sure to remove the cable from its position and thoroughly clean the metal on the cable and ground contact.

Also, check the alternator drive belt for proper tension. The belt tensioning system might have a fault. If so replace the belt tensioner.

Also, replace the belt.

Vacuum Leak Root Of Trouble

Q Recently my 2000 Nissan Maxima failed the mandated emission test. The emissions were poor at an idle but at highway speed emission levels were better.

After the test I checked the computer to find codes P171 and P174. I found a duct was off at the mass airflow sensor and reinstalled it. I also replaced the spark plugs as the old spark plugs appeared wet as if the engine is getting too much gasoline.

Now the emission levels are lower at an idle but code P171 has returned even though I cleared the computer. What's next? W.H., E-mail.

A It's time to look for a vacuum leak. Apparently the computer thinks the fuel mixture is too lean. As a result it adds more fuel to the mixture.

Check the intake plenums for leaks around gaskets, seals, vacuum lines and fittings. Also, check around the fuel injectors for leaks. Repair leaks as needed.

Anecdote For Wiper Malfunction

Q In a recent column I read about the wiper dilemma in which the windshield wipers stopped in the middle of the windshield. I had the same problem in my 1998 Dodge Caravan. Every once in a while the wipers would stop right in the middle of the windshield. The problem was repaired when the multifunction switch on the steering column was replaced.

Can you tell the other reader that this cured the trouble in my car? J.S.,

St. Paul, Minn.

A Thanks for your anecdote. Hopefully J.G. is reading the column today. You could make him a hero. The trouble was in his wife's Chevrolet Impala.

When the wiper switch was turned off the arms stopped in the middle of the windshield and blocked her view of the road.

A failed multifunction switch in your vehicle commonly causes the wipers to intermittently stop during normal operation right in the middle of the windshield. This usually doesn't occur when turning off the wiper system.

It's feasible that a failed multifunction switch on the steering column is the trouble in the Impala but usually when the switch fails in this model vehicle the wipers don't work at all. In the column you read I suggested that a switch or control module in the wiper motor had failed. J.G. should check the multifunction switch on the column although the symptoms you experienced are different from the symptoms in the Impala.

Phil Arendt is an automotive columnist, consultant and

ASE-certified master technician. E-mail him on the Web at

www.drgizmo.ws.