Vehicles are lasting longer than ever, as long as you take care of them. You might know when to change your oil, but what about the transmission fluid? If you guessed “when it starts making a grinding noise,” you’re wrong. Here’s what a professional mechanic says about changing your fluids, so you can make your investment last.


Ask five random people about when to change a vehicle’s oil, and you’ll get six different answers. There’s a few reasons people are often confused about this one.

“Oil, for a long time, was 3-months/3,000 miles,” said John Burkhauser, Director of Educational Programs at Bolt On Technology. “That was because the engines used a very basic oil that just came out of the ground, plus a few additives. Now, oil itself is a technological wonder because there’s so many additives today, it’s a totally different oil. Or it’s completely synthetic, and the oil changes can range from 5,000 to 15,000 miles.”

Burkhauser has seen a lot of changes like this first-hand. He’s a certified ASA Master Technician with over 30 years of experience wrenching under hoods, starting as a dealership tech and progressing to service manager and shop foreman, and has 10 years of teaching post-secondary.

“The thing I always say to people is these companies spent a lot of money to make sure that engine lasts through the warranty or longer,” said Burkhauser. “So they’ve done a lot of research on it.” Meaning, most of the time, drivers should follow the schedule in their owner’s manuals. But not all the time.

“That’s like saying one pair of pants is gonna fit everybody. That’s not going to happen.” Burkhauser pointed out how the vehicle interior can adapt to a four-foot tall driver or a six-foot tall driver, depending on the individual needs of the owner. The driver’s seat is not fixed in one place, and neither are oil change guidelines. Miles driven, throttle technique, and weather conditions vary for nearly everyone on the road. One size fits all doesn’t work here.

“So now we have to start looking at how often you drive, how far, and in what conditions,” Burkhauser said. “Think about a person that drives maybe a thousand miles a year. Do you want them to wait five years for an oil change? No, so there’s a lot of different factors you have to take into play, and look at what oil change works for that individual’s driving habits.”

If you go cheap buying conventional oil, stick to the lower end of the scale and change it and the filter every 5,000 miles. More frequent oil changes are also recommended when towing, racing, or driving through severe conditions, like dust storms. The higher mileage oil changes are for those using high quality synthetic oils in modern engines under average day-to-day driving conditions.


“The other one that really needs to be mentioned is the coolant, the antifreeze,” said Burkhauser. “The reason I bring that up is because many companies say it’s good for life, but it isn’t. It breaks down over time and people don’t realize that when they let it sit too long, it’s actually eating the engine from the inside out.”

Burkhauser said that the antifreeze turns acidic and starts to eat away at the metal surfaces in your cooling system. This is where coolant system leaks come from, but by the time you discover it at this point, it’s too late and has done major damage. The entire cooling system needs to be replaced, and possibly the engine. Don’t skip this one.

The Hyundai Sonata owner’s manual states the coolant should be changed at 60,000 miles, and then every 30,000 miles after that.


Some drivers never change their transmission oil, even if they own their vehicle from the dealership to the scrap yard. Like oil changes, this one is hugely variable. Toyota recommends changing transmission fluid in their automatics and CVTs at 100,000 miles, while some Jaguar cars are due at 60,000 miles, and Ford heavy duty trucks should be serviced at 150,000. Some manufacturers don’t put a transmission service schedule in the owner’s manual at any mileage, but most of them eventually need a fluid change.

“For automatic transmissions, a lot of the companies say hundred thousand miles to change the oil,” said Burkhauser. “But if you only drive 12,000 to 15,000 miles like most of us, that might mean eight years before you change that fluid.” Burkhauser likened it to the “shelf life” of perishable food. You have it in your fridge for a certain time, then you have to toss any remaining before the expiration date. With food or car fluid, there are potentially serious risks involved in exceeding the shelf life.

Get It Done

Why do we have to do this anyway? Why not just keep adding oil when it gets low and call it good?

“Fluid changes make the vehicle last an awful lot longer,” said Burkhauser. “The fluid has chemicals in it that break down over time. Plus, these fluids are exposed to some very high temperatures in the engine, and high pressures in the transmission, which too has an effect. Then there’s exposure to the atmosphere, and environmental inputs like dirt, and salt. Over time, all of these factors are going to affect the fluids’ ability to do the job it was designed for. If you don’t swap it out, it’s going to start to break down and fail, and that’s going to cause a variety of different expensive mechanical issues.”

While a bit of a time and cash investment, Burkhauser said the preventative maintenance of proper fluid changes are an investment well worth the cost. “The average car on the road is 11 and a half years old, and hundreds of thousands of miles are normal, if you do the basic maintenance.”

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