i have a 2002 impreza 2.5 auto. i know i says that the trans is lifetime oil but should i still do a trans fluid change and what oil should i use

A fluid change every 30,000 or once a year will give you long life for the trans. I believe your car takes Dexron II, which has been replaced by Dexron III. Lots of folks like the Redline fluids.

At work we ust Castrol Dextron III. I think it is 3.5 Litres from memory dont quote me or anythin. Australian shedual is every two years or 50000km

I just changed the ATF in my forester the other day. Its real easy to do yourself. Just take off the drain plug and let the old stuff flow out. Replace old plug and refill.

I got out about 5 quarts and it holds 10 quarts. My plan is to drive it for a week then do the procedure again. Ive heard that these autos cant be flushed out completely. The best you can do is get a mixture of new fluid in with the old. Something is better than nothing.Next week when I finish the job I plan on replacing the filter at the same time.

Im using Castrol Dexron III. Seems to work well and it was cheep. Im not so sure the expensive stuff makes a big diferance. If anyone knows Im wrong about this please let me know.

ATF fluid is not a lifetime fluid. Frequent changes will definitely prolong the life of the tranny.

thanks for you input....one more question should i put a synthetic atf does it really matter

just did this in my mom's ford taurus. It didn't have a drain plug, and was a real pain to drain, ATF everywhere. What I got in the bucket was black and shiny, lots of brake band slime over the pan and metal dust on the magnet. Replacing the fluid and filter, the 2nd time its been done in 198k, brought the tranny back to life. It used to hunt and shift hard, and not downshift right after flooring it, everything was fixed by a fluid and filter change. Only half the fluid comes out, the other half is in the torque converter. I believe a "power flush" changes all the fluid, but I didn't want to take any risks.