Q: I recently purchased a 2008 Chevy Equinox with 81,000 miles. It has the non-GM Aisin AF33 five-speed transmission. The owner's manual states to use only T-IV automatic transmission fluid. I pointed this out to the shop when I had the transmission fluid changed. However, they used a machine to flush out the used T-IV fluid and replaced it with Dexron VI fluid. They told me that using Dexron VI is not a problem but I read on several Internet blogs and forums that using Dexron VI can damage this transmission. I asked two Chevy dealers, an independent garage and another transmission shop and I'm getting conflicting information. I would appreciate it if you could get to the bottom of this.

A: Hey, if it's on the Internet it must be true, right? The T-IV automatic transmission fluid meets industry specification JWS3309. Here are several automatic transmission fluids that are listed as suitable for T-IV applications: Valvoline MaxLife Dex/Merc ATF, Mobil 1 Synthetic ATF, Castrol Trans-Max Synthetic ATF, Quaker State Ultimate Synthetic Multi-vehicle ATF, Pennzoil Multi-Vehicle Automatic Transmission Fluid — to name just a few. Mobil ATF 3309 is a JWS3309-spec transmission fluid engineered for this application.

Like you, I found conflicting information on Dexron VI compatibility with JWS3309-spec Type T-IV fluid. Part of the issue is Dexron VI's "backward compatibility," meaning it is suitable for transmissions using previous Dexron ATFs. Aisin specifically recommends against using Dexron III in the T-IV transmission.

Remember this: Transmission manufacturers do not manufacture or produce their own lubricants. Oil companies do. I believe we can trust the product information on specific lubricants and their compatibility with specific vehicle components. So as long as the fluid used to refill your transmission meets the JWS3309 specification — no worries.

Q: My 1986 Corvette is doing some weird things. The other night after parking the car, a few minutes later I heard a strange noise in the garage. It was the electric radio antenna going up and down on its own. I had turned off the radio and the keys were in my pocket. How could the antenna motor still be running?

A: My first guess would be a stuck antenna motor relay, which is located under the lip at the back of the rear hatch on the left side. Perhaps water intruded from the hatch opening into the relay and caused it to rust and stick.

GM service bulletin No. 882099A from 1988 says a power interruption to the radio with the ignition on can cause the power antenna to malfunction, typically ending up stuck in the up position.

I'm betting on the relay.

Q: I drive only around 3,000-4,000 miles a year. In the past I have done oil changes twice a year based on Acura's severe driving conditions recommendation. I now have a 2014 Acura TL that has a computer that tells me when an oil change is due. At the moment it says my oil is still 80 percent good, and I have been driving since the end of April and have only put 1,700 miles on the car. Should I continue to do oil changes twice a year or wait until the car computer tells me it's time?

A: My ALLDATA database shows Acura's recommended oil change intervals at 7,500 miles under normal conditions and 3,750 miles under severe conditions. Why not simplify the issue and change oil and filter once per year? That's what I do with my low-annual-mileage vehicles.

Q: Is there anything I can spray on my brake rotors for rust protection when vehicles are stored for six months?

A: I spray Deep Creep on the brake rotors of my stored vehicles. Any light aerosol lubricant should do the job of protecting the rotors from serious rust for six-month storage. To satisfy the worrywarts reading this, flush and clean the rotors with aerosol brake cleaner before driving again.