Like other vital automotive fluids, transmission fluid deteriorates over time. Hard use – such as frequent stop-and-go city driving, hauling heavy loads, trailer towing – will accelerate the deterioration. That kind of driving raises the operating temperature of the transmission, and heat puts more strain on the transmission and the fluid, which helps facilitate gear shifts, cools the transmission and lubricates moving parts.

If you do a lot of driving under high-stress conditions, you should check the transmission level more often and have a repair shop check the condition of the fluid. Transmission fluid often is red but can come in other colors, and as it deteriorates it tends to turn darker. It may also acquire a burned odor that could indicate it needs to be changed or that the transmission is developing mechanical problems. Another indication it needs changing is dirt or other debris in the fluid. 

While many automatic transmission systems do not need the fluid changed under normal operating condition until well into their service life, the nature of equipment where manual transmission may be commonly found and the service such equipment perfoms (towing, hauling heavy loads, etc.) may require that the transmission fluid be changed more often than one would expect.

A properly maintained transmission fluid will extend the life of your transmission and prevent costly repairs and breakdowns.