Q: My 2023 GV80 has a lot of bells and whistles and one of them is the engine turning off at stop lights to save gas. I noticed that the feature had stopped working so I took the vehicle back to the dealership. Two hours after my appointment time, it was returned to me with the statement that there was no error code and there were many things that could affect that feature from operating correctly. I was surprised but they offered nothing more.

At home I researched causes and decided that the battery was the most logical culprit. My battery minder confirmed that short trips brought the charge down to 52%. Once charged, the feature is back working.

I thought your readers should be aware of this easy fix. Should I return to the dealership to point out their minimal service provided?

S.K., Skokie, Illinois

A: A weak or dying battery absolutely causes the condition you describe. The automatic stop/start feature is automatically turned off to allow more important stuff to keep working. I would definitely discuss this with the service manager, who may wish to send somebody for training.

Q: The owner's manual for my 2025 Toyota Sienna has a section on fuel, specifying certain generic grades of unleaded gas, but also referring to better quality and cleaner gas, termed "Top Tier detergent" gas. Shell, Mobile and a few other brands show up on the Top Tier app directory of local retailers. Is "Top Tier" gas really something to be concerned about? None of my nearby stations (Speedway, Circle K) qualify.

B.C., Kankakee, Illinois

A: When you choose Top Tier gas, you are assured that the detergent blend exceeds the EPA minimum. This cocktail keeps the engine’s intake valves clean.

Q: I own a 2018 Hyundai Sonata. Sometimes when I park, the doors will automatically lock. Is there a way to stop this?

M.M., Easton, Pennsylvania

A: Although the procedure should be in the owner’s manual, sometimes it’s not. In most cases, you can change the setting for automatic lock. For instance, go to the touch screen, select vehicle and then select setting and then select doors. There you will find a way to activate and deactivate this “security” feature. Check with your dealer’s service manager if you need help.

Q: It's five years on my current battery and time to change it. To keep my pre-set settings last time, I connected a cable to my other car’s test port and into a 12-volt socket in mine. This worked to save all the settings in the van. Today I saw an ad in the paper selling a maintenance charger and noted I need to buy one of those for my other car, which hardly gets driven in the winter months allowing the battery to constantly need charging to start the car. Suddenly dawned on me, could I put this maintenance charger on my van battery terminals while I change the battery since the only requirement is to just keep 12 volts on the cables? Read your column every week. I learn stuff!

B.H., Hoffman Estates, Illinois

A: If you have a domestic van (or car for that matter), you need not worry about losing settings. They have a keep-alive feature. But your method will always work, even on temperamental imports. Just be careful to connect your jumpers to the cables, not the terminals. And keep the positive cable from touching any part of the vehicle.

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