Motormouth: Winter gas blends don't provide freeze protection

Q: I understand the major petroleum companies formulate their gas according to the seasons. If they formulate their gas for cold weather, do I need to also use gas-line antifreeze in my car?

M.G., St. Paul

A: The seasonal gasoline blends are adjusted to provide good starting, not freeze protection. When gas is shipped to the stations it is supposedly dry. Water in your gas tank is often the result of condensation due to temperature changes. Ice is prevented by using fuel system antifreeze. Most gasoline antifreeze products are some kind of alcohol. Since most gasoline already contains 10 to 15 percent alcohol, additional antifreeze may not be necessary.

Q: I have a 2016 Kia Sorento. As I was pulling out of my garage the rear window on the lift gate exploded into a million pieces, scaring me half to death. There was no damage to the car other than the rear windshield wiper mechanism. Meanwhile, nobody can explain what caused this. Looks to me like Kia is installing inferior glass. I'd appreciate any thoughts you might have.

J.K., Boynton Beach, Fla.

A: All automotive glass must meet Society of Automotive Engineers standards, so we can dismiss any carmaker's use of substandard glass. Yet spontaneous glass breakage does occur. Fortunately, auto glass is tempered and, as you found, breaks into countless cubes instead of sharp shards. Breakage may be due to thermal shock, a nick or chip caused during installation, body damage or occasionally from contaminants during the manufacturing process.

Q: We had a new battery installed at a local Volvo dealership. Once we got home the sunroof would not operate. We brought it back the next day. The dealership charged $135 to "recalibrate the sunroof." Were we fleeced?

A: Fleeced may be too strong a word, but you certainly should not have been charged to reinitialize the sunroof. During the battery swap, the technicians should have used a "keep alive" device to prevent power to the electronics from being interrupted. They goofed and you should get a refund.

Q: We recently bought a 2017 all-wheel-drive Subaru Forester. I have heard that after a certain amount of miles, if only one tire is damaged and has to be replaced, you must install four new tires because the difference in tire diameters between the new and older tires could damage the AWD components. If so, are there any mileage guidelines?

B.B., Countryside, Ill.

A: A rule of thumb about mileage is hard to come by. Different brands and models of tires wear at different rates. That is why it is better to measure the tread depth of the remaining tires and compare it to the tread depth of a new tire. Most owners' manuals will provide the maximum allowable variation. About the only alternative to replacing all four tires is to have the one new tire shaved down to match the tread depth of the others.