Q: Thanks for your column! It’s always full of practical advice and info. In a recent column, the reader asked how cars know what the speed limit is. My experience is that they can also use the front camera to “read” speed limit signs, and quite accurately. I know that my 2021 Ford Explorer does this because someone spray painted the sign in our neighborhood, changing the “30” into an “80” mph. My car read the speed limit as 80 mph there until the sign was fixed back to 30.

B.Q., Stillwater, Minnesota

A: Whoa! Don’t try to talk your way out of a speeding ticket. That’s an old prank. Many vehicles now read the speed limit signs, but even some untampered signs are not right. You’ve probably driven on an interstate where the posted speed signs don’t agree with a GPS speed limit. Also, the signs may be hard for the camera to see in poor weather. Somebody needs to find those vandals and make them clean the signs … or fine them $80 to cover the cleaning fee.

Q: Enjoy reading your column every Sunday and have a question for you. I have a '99 2-door Tahoe and run 265/75R16 tires. I'd like to buy a portable air inflator/compressor with a clamp style connection that I can keep in the truck. I've looked at recommendations and even called a couple of the leading brands for performance verification. Surprisingly enough, when I've talked to their reps over the phone, they're noncommittal as to whether they have a portable one that will fill a tire of my size. I'm told they're really for smaller tires but might do the job. Is there a brand/model that you would recommend that is small enough to keep in the back?

B.B., Buffalo Grove, Ilinois

A: I feel your pain. I drive a Ram 1500 with 275/60R20 tires. We’re not even talking tractor tires here, but many inflators will work — some better than others. You can retrofit some with a valve clamp-on device. Battery powered inflators are useless so opt for one that plugs into the vehicle’s power outlet (formerly the cigarette lighter). If your truck has a 110-volt outlet, woohoo. The best choice is a compressor that sits on the ground, not a handheld. It won’t fit in the glove compartment or jockey box, but it sounds like you would be content to carry in the truck bed. You will need patience. These are large tires and that means extra time to inflate them.

Q: I have a 2024 Subaru Forester. I plan to keep it for many years. The Subaru dealer says the manufacturer recommendation is an oil change every 6 months or 5,000 miles, whichever comes first. That is all they will say when I ask about my question below. I mainly drive short trips. At the first 6 months the mileage was 2,195; the next six months it was 3,800. Do I need to get the oil changed every 6 months despite such low mileage? If I don't, could that void my warranty if I have engine issues? What do you recommend?

D.S., Eagan, Minnesota

A: Subaru recommends changing the oil in most of its vehicles every 6 months or 6,000 miles, whichever comes first. And, yes, neglecting the published schedule may void your warranty. That’s why I suggest that you always keep records of oil changes if you have them done somewhere other than the dealer. It’s always good to have proof.

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