Motormouth: Gas downgrade no problem

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. It’s the same car except the 2025 has all-wheel-drive. Would it be detrimental to the engine if I used regular? I want to save a few cents, but not if it will cause engine dysfunction. What do you recommend?

A: Your engine will be fine. You might lose a bit of fuel economy with regular, but do the math against the cost of premium. 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 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?

A: Yes. 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 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?

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

Q: What is my car 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. I have assumed that this buzzing is normal.

A: It is normal. About five hours after the car is parked, the evaporate emissions system does a self-check. That’s what you’re hearing.

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

A: Yes, I have. The donor car doesn’t have to be running, but it helps if it is. Plus, if the jump requires several long cranks in the dead of winter, when the cold saps a battery’s energy, you could end up leaving the battery too weak to start the jumping car. The next thing you know, you have two cars that need a jump.

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.