Q: I have a 2010 Nissan Altima 2.5S with 131,000 miles. For normal operation, the owner’s manual vaguely states that the transmission fluid should be “inspected” every 60,000 miles. Additionally, I do not see any recommendation to ever change the transmission fluid. Thus, my questions are (1) when inspecting the fluid, is there anything else to look for other than the obvious fluid level and (2) is there a mileage threshold at which the fluid should be changed?

T.J., Chesapeake, Virginia

A: Most modern transmissions use “lifetime” synthetic fluid. Carmakers attempt to make ownership as simple as possible and have come a long way from the routine 30,000-mile flush and fill. To carmakers, a lifetime may be the life of the warranty. But I like to change the fluid around 100,000 miles, which contributes to the lifetime ownership. Inspection is to check for discoloration and debris.

Q: I have a 2015 GMC Acadia and hear a clunking noise while downshifting or when using the decel button on the cruise control. Transmission problem, I thought, but my GMC dealer said no after a complete diagnostic check. The dealer also provided a copy of a TSB entitled "Information on Driveline Clunk Noise" (July 8, 2024) that states, in part, “Dealers are discouraged from attempting to repair driveline clunk conditions for several reasons.” What is the basis for that non-repair advice?

G.S., Mesquite, Nevada

A: Near the bottom of the technical service bulletin (TSB) it says that when two or more gears interact with one another, there must be a certain amount of clearance between those gears. A stack-up of clearance or free play (also known as lash) can translate into a clunk. It’s almost never the result of one individual component. Because all the components in the driveline have a certain amount of lash, changing driveline components probably won’t reduce clunks. Noisy yes, annoying yes, but harmful? No.

Q: I’m looking to purchase a new SUV and many of the new vehicles have turbocharged engines. The dealers state that regular gasoline is OK. My new Hyundai Sante Fe is one of these and the manual specifies the 87-octane minimum requirement. Although these newer turbo vehicles have anti-knock sensors, much of what I’ve read online claims it’s not a good idea to use it 87-octane regularly but only on occasion. If I don’t want to use higher octane gasoline, should I avoid the newer turbocharged engines or do you think these newer turbo engines are OK with 87 octane during its lifetime?

A.B., Skokie, Illinois

A: Is perfectly fine to use 87-octane gas. Don’t believe everything you see online.

Q: I own a Chevrolet Trax (2018). Yesterday I used the remote start. It came on and then abruptly cut off. I thought nothing of it but then noticed the engine light on my dashboard was on and stayed on all the way to work, but the car ran fine. I tried the remote start again and got no response. How much will this cost to fix and what effect will this have if I don't choose to get it fixed?

T.B., Wayzata, Minnesota

A: Most remote start systems will automatically disable themselves if there’s an issue with the engine and the check engine light comes on. It may be as simple as a loose gas cap. You can check for trouble codes if you have a diagnostic scanner. If not, most parts stores will scan your car for free. Only then can an estimate of cost be worked up.

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