Q: Would a doughnut spare tire from a 1997 Pontiac Sunfire work on a 2014 Hyundai Elantra? Is there a standard size doughnut that works on most cars or does the size of the doughnut need to change as the year/make/model of the cars change?

P.S., Calumet City, Ill.

A: It is not as much about the size of the tire, but the dimensions of the rim. Different cars have various lug bolt hole dimensions. Some cars have five holes, some have four; the distance between holes varies, and so on. The diameter of the wheels varies. In other words, it probably won't work.

Q: Since I retired, I don't drive my car as much. What precautions should I take? Should I add Sta-Bil to the gas? Anything else? I drive about 25 miles per week. I get a tank of gas about every three months. My next 5,000-mile oil change is due in about four years.

S.D., Minneapolis

A: Adding a fuel stabilizer may be beneficial. Like a tonic, it certainly won't hurt. Don't wait years to change your oil. Change it annually at the very least. Short trips are rough on oil.

Q: At a recent oil change, my dealership performed a complete brake system fluid exchange that cost me an additional $129. I have 46,000 miles on my SUV. Was this necessary? How long could this have gone?

T.C., Bridgeview, Ill.

A: The Society of Automotive Engineers suggests changing the brake fluid every three or four years. We prefer to change it based on analysis of the amount of copper found in the fluid. The higher the copper content, the more worn-out the fluid. Professional technicians use special test strips to make the determination.

Q: I suspect I am a victim of premature battery failure. I drive a 2014 Honda CR-V on which the battery failed when it was 33 months old. I drive mainly short trips and the car had 18,000 miles on it when the battery failed. My question is, how can I know if the battery is fully charged and what can I do if it is not?

R.C., Chicago

A: If you own a voltmeter, you can measure the voltage at the battery posts. (Do not measure at the battery clamps.) Fully charged, it should read 12.5 volts. Anything less means less than fully charged. Anything below 11.8 volts indicates less than 25 percent charged. To keep your battery fully charged, especially during extended storage, use a battery maintainer — a device that keeps the battery charged yet prevents overcharging. Battery Tender is a popular brand, but any device that has a float mode will work.

Q: I have a 2015 Honda Accord and I changed the oil religiously every 5,000 miles, although the car catalog stated that it should be done every 7,500 miles. I had a problem on the Pennsylvania Turnpike and it had to be towed to the dealer. It was something to do with the universal joint. The dealer told me that the incident was caused because I did not change the oil every 3,750 miles and therefore, the warranty was not applicable. Is that possible? My total bill was $113 and for that amount I did not want to involve an attorney.

L.P., Allentown, Pa.

A: Universal joints are not lubricated by the engine oil. The joints have grease in them to keep them lubed. No, it is not possible.

Bob Weber is a writer and mechanic who became an ASE-certified Master Automobile Technician in 1976. He maintains this status by seeking certification every five years. Weber's work appears in professional trade magazines and other consumer publications. His writing also appears in automotive trade publications, Consumer Guide and Consumers Digest Send automotive questions along with name and town to motormouth.tribverizon.net.