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Q: My tire pressure monitor light is constantly on for one or more of the original tires on my 2009 Subaru Impreza with 40,000 miles. We love the car and plan on keeping it as long as possible. My repair shop said that there is a limited life on the sensors and the batteries, and I've been told that when we replace the tires (which will happen soon), we can solve the warning light issue by also replacing all the sensors.

The sensors are $80 apiece. Can I just keep an eye on the pressure like we did before these sensors existed, or do I really need to spend the $320?

A: Tire pressure monitoring sensor batteries are designed to last 10 years. It sounds as if yours died pretty much on schedule. You are not required to replace the sensors, but for your peace of mind, convenience and safety's sake, it makes sense to do so. Check around for lower prices on aftermarket ones.

Protecting plugs

Q: I have a 2002 Hyundai Accent. The spark plugs have removable terminal nuts made of aluminum. I have found that after about 5,000 miles, I notice a brief miss when I load the engine too much in lower gears. I have found that if I take an emery board and clean the aluminum tips, the problem is fixed for another 5,000 miles or so.

The aluminum corrodes as evidenced by the blackish gray on them. Is there some way to prevent the aluminum corrosion?

A: Go to an auto-parts store and buy some dielectric grease. Sometimes it is sold as tuneup grease. Squeeze a dab into each spark plug boot. Not only does it prevent corrosion, it makes boot removal easier the next time.

Sensor fatigue

Q: I have a 2017 Subaru that I bought used. On a monthly basis, the computer says that my windshield water is low. This is not true. My concern is that if that is incorrect, what else also is incorrect. My dealer brushes it off.

A: I'm with your dealer. This should not be a major concern. The fluid level sensor might be shot. Or, some washer fluid brands can contaminate the sensor.

Carbon dating

Q: Back in the day, it was common knowledge that every once in a while you had to rev up your car to burn off the carbon. Was that true then, and is it true now?

A: I'm not sure what "day" you're talking about, or if it was true then. But I am sure that it's not true now.

Wiped out

Q: Rear window wipers have become the norm for hatchbacks, SUVs and station wagons. Why aren't they on passenger cars?

A: Road scum, dust and such get on the back glass of square-shaped vehicles. Because cars are more streamlined, they do not suffer the same problem.

Bob Weber is a writer, mechanic and ASE-certified Master Automobile Technician. His writing has appeared in automotive trade publications, Consumer Guide and Consumers Digest. Send automotive questions along with name and town to