Changing the transaxle (transmission) fluid on an MR2 turbo is actually very simple. The only difficult part is removing the drain and fill plugs which can be somewhat stubborn, particularly if they have never been removed before. Click pictures to enlarge.
I have tried Mobil One, Redline MTL, and Redline MT-90, and have the best results with MT-90. The difference, in my case, was much easier shifting, no more grinding on 3rd gear up-shifts, and easier downshifts into 1st gear. I would have to say that the improvement in shifter feel was significant when using MT-90.
The first step is to remove the fill plug. While this may sound strange, it is best to make sure it can be removed before draining the transaxle of fluid. I find it easiest to jack up the car and remove the driver’s side rear tire. This makes access to the plugs much easier.
Tools used – 24mm socket.
Once the fluid is drained, replace the drain plug. To fill the transaxle, I use a funnel, a tube (from Home Depot) and some duck tape.
Run the tube through the engine compartment and down into the filler plug. Then place some sort of oil pan / bucket under the filler plug to collect any excess transaxle fluid. You want to fill the transaxle until fluid starts to run out of the fill plug. Make sure the car is level when filling – it usually takes 4 quarts, sometimes a touch more.
Tube inserted into fill plug:
Then just start adding fluid to the funnel. If it is particularly cold when performing the fluid change, it can help to warm up the gear oil by bringing it inside, or even putting it in an oven at very low heat. Wives love it when you do that! This will help it pour and drain into the filler more quickly. It does take time.
Allow any excess fluid to drain from the filler plug, replace the filler plug, and your done! I usually replace the fluid once per year, and have been using Redline MT-90 for about 6 years now.