Do automakers always tell the truth? An expert says “not always.” Chris, who works at Beachside Automotive Parts, took to TikTok claiming that your owner’s manual may be lying about two important maintenance intervals. These are fluids you should be checking—and even changing—more often than the book in your glovebox recommends.

1. Transmission fluid ‘for life’

“A lot of modern vehicles, including trucks like the newer F-150, say their transmission fluid is filled for life.” I know Ram 1500s with the 8-speed auto from ZF make the same claim. And that transmission is the most reliable part of a fifth-gen Ram 1500. So buy it and forget about it? Chris disagrees.

“That doesn’t mean the fluid lasts forever, it just means there’s no dipstick and they hope you won’t ask questions. But if you tow, haul, idle in traffic, or drive in hot climates, your fluid breaks down fast. Heat kills transmissions. Once the fluid loses viscosity and shear strength, internal clutches wear and metal shavings build up.”

So what does Chris recommend? “These sealed units still have a drain and fill plug. You just have to know where to look. If you want your transmission to last, change the fluid every 60,000 to 80,000 miles. Don’t wait for failure to find out the manual was wrong.”

2. ‘Coolant lasts 100,000 miles or 10 years’

Chris explains, “A lot of cars—Toyota, Honda, Hyundai—say their coolant lasts 100,000 miles or 10 years.” But he argues it’s an optimistic estimate. “That’s in perfect conditions, not real life. Heat, humidity, short trips—all of it breaks down the corrosion protection. When that happens, you’re looking at clogged radiators, failed water pumps, even head gasket issues. And by the time you notice a problem, it’s way too late.”

So is it worth draining your radiator? Chris argues, “Coolant is cheap. Flush it every 5 years or 60,000 miles and avoid a $2,000 repair.”

I’ll add that as an auto parts salesman, Chris has a vested interest in you swapping out your fluids. That said, diesel mechanic Justin Wheeler ran a fifth-gen Ram 1500 pickup truck to 200,000-plus miles. His motto: “Take care of your truck and it will take care of you.”

MotorBiscuit has reached out to @ChrisAtBeachside on TikTok for comment. You can see the original TikTok video embedded below: