A vehicle's transmission fluid is necessary because it keeps moving parts lubricated and helps the transmission maintain an optimal temperature. In an automatic transmission, the fluid also supplies hydraulic pressure and friction for the internal parts, so they operate correctly and smoothly. Since the gears work and shift differently, the correct type of transmission fluid depends on whether your car has an automatic or manual transmission. Even after those two categories, you will find there are many different types of transmission fluid. Aside from traditional formulas that are crude oil based, The owner's manual should specify the best type of fluid for your car's transmission needs. There are a few variables when it comes to how frequently you need to change your transmission fluid. Those variables will depend on the age or model of your vehicle, the type of transmission, what the vehicle is mainly used for, and the specific manufacturer's recommendations. If you drive an older vehicle, more than 10-15 years old, and the miles are racking up, a transmission fluid change every 50,000 miles would probably be a good rule of thumb. If you drive a more modern vehicle, refer to the owner's manual for a general timeframe, then go from there. Think about how the vehicle is used and how hard that use works the transmission. If you use the automobile for everyday errands, commuting to work, and taking the kids to school, it is likely you may not need to change the transmission fluid ever, but perhaps one or two times at the most. However, if you use the vehicle for a lot of towing trailers, hauling equipment, off-road driving, the transmission is having to work twice as hard, so it is a good idea to have the fluid changed twice as often. If you are unsure about the last time your car's transmission fluid was changed, or if you are noticing anything uncommon going on with your car's performance, bring it to Rainier Automotive so our certified expert mechanics can pinpoint the issue, repair it, and get you back on the road.