Why YSK: Most people are generally pretty good at having their engine oil changed. It comes up somewhat frequently and most people understand that not doing it on time can mean costly engine repairs.
You know what's just important to the proper function of your car, requires routine maintenance, and is also expensive to repair? Your transmission!
Newer cars are much better at telling you or the service shop what needs to be done to the car, and a service shop can read a code and tell the car needs the transmission fluid swapped. Dropping that $100+ extra needed cost on a customer can freak them out a bit, especially if they only went in thinking they were getting a $50 oil change.
As a car owner, know your service intervals! You should find it in the manual, but you can look online, too. In most cases, transmission fluid should be changed every 20,000-50,000 miles, depending on what you're driving and how you're driving it. If your drives are mostly short drives, your fluid will need more frequent changes. If you're not sure, do it every 30,000, and you'll be pretty safe. Once your transmission fluid has darkened, it loses its lubrication and heat dissipation properties. Excess heat and friction kills transmissions. Additionally, your transmission is filled with tiny parts and valves, and clumps of dirt and gunk in the transmission fluid can gather and settle on these parts and valves. Replacing your fluid regularly will keep this buildup from happening, extending the life of your transmission.
But if your car has 100,000 miles on it, and the fluid has never been changed, do not have the fluid changed and definitely do not have it flushed. If you've driven several tens of thousands of miles and never had that fluid changed, you're now dealing with stable chaos. There is likely already gunk settled in places it shouldn't be, but if the transmission is working fine at this stage, replacing the fluid will break some of that stuff free, and then you can run into problems faster than if you hadn't changed it at all. You can have rough or delayed shifts. You might even lose gears. At this point, your car is the equivalent of a paper cup. Use it for as long as you can, then get rid of it.
A transmission fluid change or flush can be $100-200 so knowing your intervals will help you plan for the expense. A whole transmission can be well over $1,000 before the labor costs. All in, you could be looking at spending at least $2,500 for the job, at which point, you might as well buy a newer car. A transmission fluid change is so infrequent, too. Most people will need it done to their cars no more than 2 or 3 times before they get into something newer.
Save yourself or the next person to own your car the heartbreak and keep this oft overlooked piece of machinery maintained.
