At this point its probably wasted money. Its more important to flush it regularly rather than to use synthetic or not. Sure if money is no object the synthetic is a better fluid but I doubt you're gonna realize any overall benefit from it now. If you're looking for piece of mind or you only want the best for your Volvo use the synthetic. My wife's '95 850T only has 21k miles on it and I switched to Mobil One synthetic when I changed the fluid last year. But the car gets such little use I did it more for piece of mind than anything else. There's no internal filter in the 850's tranny so regular changes are crucial to the longevity of the tranny. Good luck ....... Mike