Q: After Christmas dinner my brother and I had a disagreement regarding if it is best to turn off all accessories in the car before turning off the car. My sister-in-law and I both turn off the heater, radio, etc. before turning off the car. Who is right?

P.H., Chicago

A: Your brother wins. When you turn the key (or hit the engine start/stop button), all of the accessory circuits are also turned off. There is then no drain on the battery thereafter.

Q: Does it weaken the car's battery if the headlight (not daytime running light) switch is in the "on" position when the car is started?

E.P., Audubon, N.J.

A: The battery remains unaffected if the headlight switch is left on. When the key is turned (or the engine start/stop button is pushed), the headlight circuit is temporarily bypassed. This is designed to provide maximum battery power to the starter.

Q: In the foggy distant past, it seemed that the radiator coolant was changed annually. My 2012 Toyota Corolla's coolant has been checked but never changed. Am I headed for trouble? How often should the coolant be changed?

T.P., Milwaukee

A: In the very distant past, antifreeze was methanol (methyl alcohol). It did an adequate job until the weather warmed and radiator boiled over. The mix was then drained and replaced with plain water. The term permanent antifreeze was coined when the ethylene glycol-based product was introduced. "Permanent" meant that the coolant (antifreeze plus water) could be left in the system year-round, but usually had to be replaced every couple of years as the additives wore out. Today, long-life coolants are typically changed every five years.

Q: Do any new cars come with a dash cam? It makes it easy to prove who is at fault in an accident.

E.G., Collegeville, Pa.

A: We are not aware of any cars offering a dash cam, even as optional equipment. But they sound like a good idea, especially when saving the files to a flash drive for safekeeping. In Russia, almost every driver has one to provide proof of fault (or not) in accidents.

Q: I have a six-cylinder 2017 Kia Sorrento which always reports average miles per gallon as somewhat higher (say, 2-3 mpg higher) than my calculation with a calculator. Is this just "marketing math" (the car computer programmed to calculate high), or is the higher number genuine?

M.D., Schererville, Ind.

A: About five years ago, Kia (and Hyundai) were accused of overstating their fuel economy ratings. As a result, the companies offered settlements via gift cards to cover the calculated expense to owners. With that in mind, it would be suicide for them to overstate the fuel economy numbers.

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.