Q: I drive a 2019 Acura MDX A-Spec with a 9-speed automatic with sequential sport-shift paddle shifters. Can using the paddle shifters harm the transmission? I use the paddle shifters to shift up for gas efficiency.

— B.S., Oswego, Ill.

A: The shifting in an automatic transmission is activated by solenoids that receive a signal from the electronic control module. When you tap the paddle, you send a similar signal to the solenoids, overriding the calculated computer shifts. Short answer: You are doing no harm. But short-shifting may reduce fuel economy. Also if you attempt a shift at the wrong time, it will be disallowed.

Q: When I asked a friend why he fills his 2016 Hyundai Accent with premium gas, he said by doing this he gets more miles per gallon compared to regular gas. He also maintains that regular gas is too watery. Is my friend right?

— J.C., Fort Lauderdale, Fla.

A: He is wrong. Burning premium gas in a car that calls for regular just burns money. Neither fuel economy nor performance will improve. Likewise, if premium fuel is recommended but not required, most motorists will see no difference in performance and the engine will not knock or ping on regular. Ask your friend to buy you a beer with the money he saves.

Q: I tried Rain-X several years ago and found it to be effective. However, on a sunny day, driving west in the late afternoon, the rays of the sun coming through my windshield were highly refracted, causing nearly total loss of visibility. I pulled over and scrubbed off the Rain-X and the problem was fixed and did not return.

— F.C., Chicago

A: I had not heard this before, but I will keep an eye on it. I have heard rumors that Rain-X can also play tricks on some rain-sensing wiper systems and washer fluid level sensors.

Q: I never really used glass treatments. What I’ve used for many years is a brass blade scraper that works unbelievably well for ice and frost removal. It’s much thinner and stronger than plastic. I bought my first one many years ago from Ace Hardware, but now only find them online. I’ve bought the Snow Joe brand for everyone in my household and they all love it. I must be careful not to hit any painted surfaces, though.

— K.B., Chicago

A: I received a brass blade ice scraper for testing last year and agree with you. It is helpful to also have an additional ridged edge to break up heavy ice coatings. Watch out for rubber gaskets as well as paint.

Q: Reading the trouble code and changing that part isn’t always the fix. I had a 1998 Econoline with a code that said “bank 2 sensor 2.” But replacing the oxygen sensor was not the fix. It turned out that there were two rust holes in the front cat. I dealt with and them and the vehicle passed its test. You can’t just replace what the code reader says every time.

— J.M., Waukegan, Ill.

A: I couldn’t agree with you more. Yes, parts stores will loan out a code reader and will usually look up the code. They are also happy to sell you a new part, but as you discovered, that is not always what you need. The fault could be anything from a dirty connection to a bad ground. You need a professional auto technician to not only interpret the code but hunt down and fix the underlying problem.

———

ABOUT THE WRITER

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 questions along with name and town to Motormouth, Rides, Chicago Tribune, 435 N. Michigan Ave., Fourth Floor, Chicago, IL 60611 or motormouth.tribune