The manual transmission fluid recommended for Mitsubishi vehicles is Mitsubishi Genuine Fluid. An automatic transmission fluid of the same name is recommended for Mitsubishi vehicles with automatic transmissions.
Changing manual transmission fluid is recommended to maintain a smooth transition between gears. Manual transmissions running dirty fluid often exhibit loud noises when shifting gears, and the gears eventually become damaged.
Automatic transmission fluid lubricates and provides power to the transmission. Automatic transmissions that need the fluid changed experience similar problems as manual transmissions in the same condition. However, in addition to damaged gears, the vehicles use more fuel, and the transmission has to work harder to shift on its own.
To determine whether the transmission fluid needs changing, allow the vehicle to run for a few minutes. Pop the hood, and use the dipstick to check the oil level and color. Transmission fluid should be a transparent red. If the dipstick shows this color but reads a low level, simply add more fluid. If the color is dark or dirty, the transmission fluid needs changing.
Before changing the transmission fluid, raise the vehicle using ramps or a jack. Find the transmission pan, and position a receptacle underneath it. Unscrew the bolts, and allow the transmission fluid to drain. Examine the transmission's gasket. If it shows wear, replace it. Take out the filter after all the fluid has drained, and replace it with a new one. Put the bolts back on the transmission pan, and lower the vehicle to the ground.
Pop the hood, and add the new transmission oil using a funnel. Turn on the car, and let it run for a few minutes. Shift the gears several times, and then put it back in park. Check the fluid level again with the dipstick, and add more if necessary.