A mechanic draining the old, brown automatic transmission fluid from under the car - PongMoji/ShutterstockThe color of your car's automatic transmission fluid (ATF) can tell a lot about the general health and condition of the transmission. All automatic transmissions, whether you have a continuously variable transmission (CVT), dual-clutch transmission (DCT), or a conventional automatic, need fluids to operate smoothly and protect the internals from premature damage. But unlike engine oil, which requires more frequent draining and replenishment, the ATF can last 60,000 to 100,000 miles before needing a flush. Then again, the intervals will depend on the type of vehicle, driving conditions, and more.And that's the problem with modern automatic transmissions. Since it's known to last longer than engine oil, the ATF is one of the most neglected fluids in the car, especially when manufacturers realized that the ATF dipstick is hilariously redundant. If your car doesn't have a transmission dipstick and the odometer reading is past 60,000 miles, it's high time to visit the dealership or your neighborhood garage to check the fluid.Otherwise, park the vehicle, turn off the engine, open the hood, and grab a lint-free rag. Pull out the ATF dipstick, wipe the end clean with the rag, reinsert the dipstick fully into the filler neck, then pull it out again. At that point, there are three things to check: oil level, color, and odor. The level should be anywhere on the HOT or COLD markings of the dipstick. Meanwhile, the color should be bright red, dark red, or slightly brown, and it should have a mildly sweet and oily petroleum scent. If the fluid is black, slightly pinkish, or a deep, dark brown, it's time to flush the ATF at the soonest possible time.AdvertisementAdvertisementRead more: 5 Nearly Indestructible Transmissions (And The Cars That Use Them)Dark ATF and a burnt smell are a bad combinationOld and contaminated ATF leftovers in the transmission oil pan of a car - Setta Sornnoi/ShutterstockIf the ATF color is within the reddish to brownish range and the fluid smells rather good, you're in the clear. The best you can do is check the fluid level and replenish it with the right type of fluid. Not all ATFs are the same, and some might refer to DCT or CVT fluid as ATF. Dual-clutch transmissions require special DCT fluid, and CVT fluid is different from ordinary ATF. To avoid confusion, refer to your car's owner's manual to know which type of ATF is best suited for the transmission.On the other hand, black or dark brown ATF is a serious concern. It means there's heavy contamination and that the fluid has severely oxidized, rendering it almost useless in lubricating, protecting, and managing friction inside the transmission. If left longer, dark ATF can damage the transmission and lead to enormous repair bills, since low or contaminated fluid is one of the leading causes of transmission failure. It's imperative to drain the ATF or bring the car in for servicing immediately. In most cases, the transmission will also need a filter change to make the most of the fresh, new fluid.Pink or diluted ATF is bad newsA car owner opening the radiator cap to check the coolant level - Virojt Changyencham/Getty ImagesThere are cases when a supposedly bright red or dark red fluid can turn a hazy shade of pink, and it typically means water or coolant has infiltrated the transmission. That's not good, since that same mixture can enter the coolant passages inside the motor and cause another set of problems, like overheating, for instance. There's an ATF heat exchanger in the radiator's bottom to regulate the fluid's temperature. And even though the coolant and ATF lines are separate, an old, rusted, or leaking radiator can mix the two fluids and wreak havoc on everything.AdvertisementAdvertisementYou'll most likely need more than just a transmission flush if you find pink ATF on the dipstick. A new radiator or fluid cooler might be in the works. The worst-case scenario is transmission damage, since nobody can tell how long that pink, contaminated fluid has been circulating in the engine and transmission.The best thing you can do to prolong the service life of any automatic transmission? Apart from avoiding the nasty driving habits that are wearing out the transmission, periodically checking the ATF color and fluid level (preferably every 30,000 miles) will keep you in touch with the transmission's health and operating condition. Doing so before symptoms like grinding noises, slipping gears, surging, and difficulty shifting begin to manifest will save thousands in future repair bills.Want more like this? Join the Jalopnik newsletter to get the latest auto news sent straight to your inbox, and add us as a preferred search source on Google.Read the original article on Jalopnik.