Q: I have a 2024 Audi A3 that uses regular gas. When I bought a 2025 A3, I was surprised that it recommended premium gas. Same car except the 2025 has all-wheel-drive. Would it be detrimental to the engine if I used regular or mid-level? I want to save a few cents, but not if it will cause engine dysfunction in the future. What do you recommend?

S.G., Highland Park, Illinois

A: Your engine will be fine. Knock sensors will see to that. Sure, you may lose a bit of fuel economy with regular, but do the math against the cost of premium. According to Gas Buddy, gasoline prices average $3.40 per gallon in Illinois. The average difference between regular and premium is usually around 15%.

Q: I have a 2018 Honda Accord with a 1.5-liter engine. I have been using synthetic oil since the car was new and change it every 5,000 miles. The car has 60,000 miles on it. Can I extend the oil change time using the maintenance minder percentage indicator?

B.B., Easton, Pennsylvania

A: Yes, you may. Car makers set up their maintenance intervals carefully. That said, I like to over-maintain, but just by a little. When the oil change monitor says 30%, I get ready to change my oil soon.

Q: I am the owner of an Infiniti l35 purchased by me in 2004 with 23,000 miles and I love this car. Is my car considered "antique," and do I still need the city of Chicago and state of Illinois stickers? I drive a couple of times a week to get groceries.

H.B., Chicago

A: Cars qualify for antique plates if they are older than 25 years and basically stock— no mods. The tags must be renewed every five years. You still need a Chicago city sticker if your car is your daily driver.

Q: I have a 2014 Toyota Highlander with 48,000 miles. The brakes/rotors were replaced at 40,000 miles. They squeal in reverse and sometimes in drive. A shop said they could not find a problem. The car is garaged and is driven in town only a few times per week. What could cause the squeal?

T.J., Chicago

A: Light surface rust can form on the brake rotors of cars that are not regularly driven. The problem is worse with high humidity and near the shore. Apply the brakes a few times when you first head out and the noise will likely stop … until the next time.

Q: I have been meaning to ask what my car is doing when it makes a buzzing sound at night. Today it made that sound at about 10 p.m. My car is a 2017 Toyota Highlander, and I do not have any known problems with it and so I have assumed that this buzzing is normal.

D.S., Addison, Illinois

A: Yes, the buzzing is normal. About five hours after the car is parked, the evaporate emissions system does a self-check.

Q: Have you ever heard of anyone jumping a dead battery with the car used for the jump not started?

B.F., Virginia Beach, Virginia

A: Yes, I have. The donor car doesn’t have to be running, but it helps if it is.

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