Regardless of what they say, I say it NEEDS it. I was having shifting trouble with mine just a couple of months ago. It was shuddering when shifting from 3rd to 4th at cruising speed. The service department said they found nothing wrong. After reading other folks suggestions here and on swedespeed, I asked them to flush it and refill with synthetic. They did and even the tech was impressed at the difference it made. He thought there was no problem with it until it was fixed, then realized what it was doing before. I was even amazed because I thought it was just having a problem in high gear, turns out it was shifting poorly between all the gears. Its like a whole new car now. by the way, mine is a '98 T5 auto with 75K miles (had the service performed at 72K). I now plan to have this done at 100K and every 25-30K after that.