Q: In response to a recent question, you indicated that automobile displays of speed limits are GPS mediated. While that may be true, an SUV we had would consistently read an exit ramp speed sign on Minnesota Route 62 at 169 mph. Even more interesting, the car would decelerate as we passed a County 50 road sign.

P.H., Edina, Minnesota

A: Yeah, some vehicles mistake route numbers for speed limit numbers. Like me, they may be a bit numerically dyslexic. Or, perhaps, a remedial reading class is in order. Thanks for the chuckle.

Q: I recently took my 2018 Buick Encore with 44,000 miles in for an oil change at an all-purpose auto repair facility. The service manager advised (and showed me) that my coolant level had dropped about 2 inches below the fill indicator line on the reservoir, and that as a result, I should get a complete cooling system flush. He explained that there might be acidity in the coolant, which could ultimately corrode internal engine parts. My owner's manual recommended this service at 100,000 miles.

D.B., Winfield, Illinois

A: I would top off the coolant with some premixed stuff. Then I would check the coolant reservoir regularly. The level is usually higher after running the engine due to expansion. The next morning, it will be lower as the coolant is sucked back into the cold engine. If you keep adding coolant, have the cooling system checked out. The service manager is right that worn out coolant can lead to internal engine problems, especially the water pump.

Q: I bought a 2024 Ford Maverick hybrid truck in July 2024. It has 3,000 miles on it so far and I was wondering when it should have its first oil change. Since the engine is running on the battery part time, how do you figure the miles it has actually driven in a year? The owner's manual doesn't say anything about it. I hope you can answer me on this.

R.D., Yorkville, Illinois

A: It is often hard to give up control and allow the vehicle’s oil life monitor to let you know when it’s time to change the oil. But that is what you should do.

Q: I own a 2021 BMW 430xi. It has almost 8,000 miles on it. Several months ago, the warning sign came up and it indicated my oil needs to be changed. My husband insists it does not. I had it changed about two years ago, before the warranty expired. When I contacted the dealer about it, they said the oil is "old" so, yes, it needs to be changed. My husband insists it does not. Of course, the warning sign appears every time I drive, which annoys me and worries me that I am causing harm to the engine due to my husband's stubbornness. Who is right here?

D.I., Dyer, Indiana

A: BMW uses a condition-based service system; it monitors the condition of the oil. The CBS system tracks your oil’s life based on mileage, the amount of fuel consumed and an oil quality sensor in the oil pan. Trust it when it tells you to change the oil.

Q: I have a 2018 Subaru Outback with 112,000 miles on it. I take very good care of this car and faithfully follow the manufacturer’s maintenance recommendations. The dealer tells me that I need to replace the timing chain at 120,000 miles. Other sources inform me that I never need to replace the timing chain. What’s your thought about this?

C.H., Cologne, Minnesota

A: The timing chains on the FB25 engines are maintenance-free.

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