If you have an automatic transmission you need to flush and fill the oil every 24,000 to 30,000 miles. More often if you tow. You also should install an aftermarket external transmission cooler. Do not be fooled by Long Life Transmission Fluids. The heat in transmission fluid from stop and go traffic can really shorten the life of your transmission, as well as towing. Do not be suckered in to "the car has a towing package". Please double check to make sure ther is an external tranny cooler (pic below). Most OEM transmission coolers use the bottom of the cooling system main rad to supposedly cool the transmission. With newer hotter engines, normal cooling system thermostats are run between 190 and 195 degrees. At 195 degrees of your transmission fluid life is reduced to half it's life (50,000 miles of highway driving for a top notch fluid). At 220 degrees, which is commonly encountered in many transmissions, the fluid is only good for about 25,000 miles. According to the Automatic Transmission Rebuilders Association, 90% of ALL transmission failures are caused by overheating. An auxiliary transmission fluid cooler is easy to install and can substantially lower fluid operating temperatures. The plate/fin type cooler is somewhat more efficient than the tube and fin design, but either can lower fluid temperatures anywhere from 80 to 140 degrees when installed in series with the stock unit. Typical cooling efficiencies run in the 35 to 50% range.

My automatic 6 speed Aisin Warner transmission lasted 20,000 miles, then I needed another one (under warranty). After this I installed an external tranny cooler (first pic below is mine). I don't tow anything. It's still working good.
Some have to be mounted in front of the cooling system rad, some can be mounted underneath attached to frame (for example) like the 3rd pic.

FROM: Transmission Fluid Life
and: Flush it or Forget it | MotorWeek
and: Transmission Talk | MotorWeek
and my own experience.

 

Spectre now has finned polished aluminum universal single pass automatic transmission coolers that comes in 3 lengths (12” #5466, 15” #5467, 18” #5468). Spectre Performance transmission coolers include two 3/8 inch NPT fittings.