Q: This past summer I drove on several roads only to discover that road crews tore away part of the road, making the tires rumble. What were they doing?
A: What you describe is milling. The first couple inches of the road surface is removed in preparation for a new surface. Although it feels weird to drive on, the surface neither damages nor reduces the life of tires.

Keep things clean

Q: I'm a light-footed original owner of a 2017 Subaru Impreza with 24,000 miles. During a recent oil change at my Subaru dealership, the technician recommended a complete fuel induction and throttle body cleaning to prevent carbon buildup on intake valves. Estimate: $145. I refused the service. In your opinion, was this recommended work, with no other indications than mileage, a good idea?
A: Unless you have been using no-name gas, the intake valves probably don't need cleaning. But throttle body cleaning is a legitimate service. The quote was not out of line, so I suggest you approve the service the next time you have the oil changed.

Plug it up

Q: My 2014 Toyota Highlander has 161,000 miles on the original spark plugs. The car runs fine and is getting 22 mpg with a V-6. My service guy recommends changing the plugs. Do you agree?
A: The replacement schedule for platinum-tipped spark plugs is generally 100,000 miles. You might not feel much difference in performance, but a fresh set of plugs can improve starting, especially in colder weather. It's not cheap, but it's worth doing.

Good idea, almost

Q: Why don't car manufacturers tint windshields the way eyeglasses are tinted for transition lenses?
A: Because it's against the law. The Department of Transportation has strict regulations about how deep the tint on windshields can extend. I have a hunch that transition technology, no matter how convenient for the driver, would never get approval.

Keep eye on leak

Q: I have a seven-year-old Buick La Crosse with 80,000 miles. During an oil change, the mechanic indicated a rear main seal leak as a "caution" item. The service writer at the dealership and a NAPA clerk both said that it was not a problem at this time. (There's no oil spot on the garage floor, and no noticeable oil level drop between changes.) The quote was $4,600. or almost half the value of the car. What is your opinion of the situation?
A: Both your mechanic and the parts store guy are right — at least for the time being. When the seal begins leaking, it does so mostly while driving. That's when you will begin seeing evidence. At the first sign of leakage, use some rear main seal leak stop. It could buy you some time. Keep up with your oil change schedule.

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 motormouth.tribune@gmail.com.