Q: When I asked a friend why he fills his 2016 Hyundai Accent with premium gas, he said that by doing this he gets more miles per gallon compared with regular gas. He also maintains that regular gas is too watery. Is my friend right?
A: He’s the one who is all wet. 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.
Q: I drive a 2019 Acura MDX A-Spec with a nine-speed automatic with sequential paddle shifters. I use the paddle shifters to shift up for gas efficiency. Can doing that harm the transmission?
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’re overriding the computer shifts. Short answer: You are doing no harm. But short-shifting — changing gears before the car reaches the speed that activates the control module — can reduce fuel economy.
Q: As part of your ongoing conversation about Rain-X, I tried it 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. When I pulled over and scrubbed off the Rain-X, the problem was fixed and did not return. Have you heard of anyone else having this problem?
A: I had not heard of this before, but I will watch for it. I have heard rumors that Rain-X can also play tricks on some rain-sensing wiper systems and washer fluid level sensors.
Decoding the confusion
Q: Reading trouble codes, changing that part isn’t always the fix. I had a 1998 Econoline with a code that said I needed a new oxygen sensor. But replacing it did no good. I eventually tracked down the problem, but I learned that you can’t blindly trust the code reader.
A: I couldn’t agree with you more. Professional auto technicians not only interpret the code but hunt down and fix any underlying problem.
Dump, don’t pump
Q: Have you had any experience with the Leixio oil pump? I contacted the company, and they told me I can use it to pump out transmission fluid.
A: Pumping (siphoning) the oil or transmission fluid is fine in a pinch. But draining the oil by removing the plug allows sediment to also drain. That is a plus. Ditto for removing the transmission pan and changing its filter.
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 email@example.com.