Fluid exchanges on 16-year old car - Ill-advised?

2007 Chevy Malibu, Automatic Transmission, 6-cylinder, 3.5l, 40k miles

Hey, so this is kind of a two-for-one, but they share a common thread, so hopefully this is acceptable, I felt it was better than two separate posts.

I recently inherited this car from my grandmother who passed in August 2022. Luckily, she always changed the oil at least once a year, even though she hardly drove it. I want to keep this thing in the best shape I can.

As such, the Owner’s Manual calls for a transmission fluid and filter change every 50k (under certain conditions, but I see no reason to not do it at that interval regardless) and a coolant exchange every 50k or 5 years, whichever comes first.

Now, I know the trans hasn’t been touched and I’m fairly certain the coolant has never been changed either. My question is: Is it a good idea to change these fluids after 16 years of them not being changed? I’ve heard that doing so could possibly introduce issues where there previously were none and you just need to kind of live with it at that point.

I’m torn because the car shows no leaks in those systems or performance issues, so I would hate to suddenly cause problems, but I also want to keep up with the maintenance and maybe get 200k out of this puppy.

Thanks all!


It’s a good idea to change all fluids now with the correct type. Transmission, coolant, brake, and power steering (if it doesn’t have electric power steering). Also the air filter and cabin air filter.

edit - those stories of problems with fluid changes often are where there’s already a problem and the fluid change doesn’t help, or where the car is already old and neglected and something major breaks after the fluid change that would have broken anyway, or where the wrong fluid was used, causing a problem. VERY few situations where the fluid change actually caused a problem.


I second that… change all the fluids, especially brake fluid.


I third it… Change all the fluids


Here’s one more thing to check - how old are the tires? If 10 years or more I’d replace them, or if worn, of course.


Don’t count on that. This wasn’t GMs best engine.

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Lots of complaints about the steering system. Not a need to sell, but be aware of it: 2007 Chevrolet Malibu Problems, Defects & Complaints (carcomplaints.com)

Yes, change the transmission fluid and filter now (use the manufacturer-specified transmission fluid, not a “universal” substitute), change the engine coolant (use a universal pre-mixed coolant, such as Prestone or Peak Extra Long-Life, rather than Dex-Cool) and change the brake fluid.

I don’t see a problem using Dex-Cool as long as manufacturer’s instructions are followed and Dex-Cool was the original coolant.

@apagodz, take. Look at all the rubber parts like hoses and belts. They may have degraded over 16 years and may need replacement soon. This is especially important for the coolant hoses since you plan to replace the coolant. If a hose fails after you change the antifreeze, you will likely replace the coolant again along with the hose.

The problem with Dex-Cool is that if a leak occurs, and air is drawn into the system, Dex-Cool forms a sludge which will plug up the radiator, heater core, etc. Other coolant types do not have this problem. I would eliminate Dex-Cool from any GM vehicle that I would own.


Yes, yes, change fluids but I’d put coolant and transmission ahead of brake fluid, but yeah just get everything up to date.

I have had no problem with dex though. When I bought my car in 2010, I wanted the dex removed but the dealer talked me out of it. When I had my hoses and coolant changed, the shop owner recommended continuing with dex which I did. I have an appointment again to change coolant and will go with dex. I have had no problem with it myself. Also have had no problem with my 3.5 in 170,000 miles but I change oil every 3000 miles and never uses any oil. But then I’ve never had an engine problem in a gas engine in over a million miles, but I don’t fudge on oil changes. Diesel was another matter. Just my experience.

Definitely change the fluids. You will not hurt a thing and only help extend the life of the car. GM may allow for a full synthetic ATF to be used in the transmission as well. If you are paying for the service, a slightly more costly fluid shouldn’t bump the overall cost by much. I don’t know the best opinion on Dex Cool as I hear some say to stay with it and others saying to dump it and use universal (yellow-green).

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A bit idealistic, I know, but I figure it’s worth a shot.

Thank you all so much for weighing in and for the further insight on type of coolant. I wasn’t expecting much response on a kind of generic question and I hope it wasn’t overly self-evident. I only have a bit of knowledge because I worked as an apprentice tech at a Subaru shop for almost a year.

I certainly feel much better moving forward with this many votes of approval!

It’s entirely possible some problem will occur following the fluid changes. If that happens, provided the fluid changes were done correctly, it was going to occur soon anyway. Sort of like if you eat some potato chips today, and tomorrow you discover your leaf blower doesn’t work. Potato chips didn’t have any effect on the leaf blower, the sequence was just a coincidence. Suggest to focus your attention on finding a shop who has the experience and technical know-how to change the fluids properly on your car. Ask friends, coworkers etc which shop they use.

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Another plus for changing all the fluids…

BTW a drain and fill of the radiator is not a flush, so if changing to a non Dex-Cool coolant make sure to flush all of it out… I’m another one for getting ride of Dex-cool… Seen a simple water pump leak not repaired properly clog up a radiator causing the transmission to over heat and fail… In a perfect world Dex-cool works as intended, but how many of is live in a perfect world??

But I would only use the correct transmission fluid as using the wrong fluid can cause poor lubrication, overheating, and possibly transmission failure

Changing your fluid cannot cause any damage by itself, if everything is fine inside the transmission. The issues start to appear when you change the fluid if your clutches are already worn or damaged from use. If you go and replace the fluid after they are already worn out. this can cause slipping…

How do you know if the clutches are already damaged or worn from use before changing the transmission fluid, if changing it will cause slippage?

The stories you’ve been told, that the engine will have problems with new fluids, are just a bunch of nonsense that people like to believe so they can save money and time with an old, neglected car.

That said, if you can figure out who actually did the oil changes, it wouldn’t hurt to ask if your grandmother had some of those other services done, too. Lots of mechanics will recommend those routine things to their regular customers, and oil change places push them pretty hard.

Look at the color of the fluid, smell the fluid,… And worst case, drop the pan and use a transmission drain pan to catch all the fluid that comes out and then see what all is in the pan… An experienced transmission builder can tell the differences in materials in the bottom of the pan, like friction material, variety of materials, such as bronze, steel-backed babbitt, plastic, nylon, or cast iron, parts of snap-rings etc etc… You can feel the grit from the clutch friction material…

You can put the old fluid right back in it if it looks like it will require a rebuild… Done it many times when a customer didn’t want or have the budget to rebuild the transmission…

In that case, instead of changing the fluid and dropping the pan and seeing what’s in there, maybe wait until the transmission dies and rebuild it completely? After going through all the effort to drop the pan and maybe have a slipping transmission after, maybe just run it as long as it shifts smoothly? Could be many years until there’s a problem like slipping?