I changed the fluid in my 5-speed '96 R last year. Used MTL and have been quite pleased with the shift quality and this despite having a short shifter on the car. One clue on the change process, make sure the car is level when you check the fluid level. The bloody level plug is located such that if you have the front end lifted at all, a fair amount of fluid just comes pouring out of the transmission giving you an inaccurate indication of oil level.

I had the manual transmission fluid changed in my 1999 V70 by my mechanic at about 45,000 miles. He used the genuine Volvo transmission fluid, which we ordered at the dealer. It shifts the same as before, no obvious change in feel.

I plan to soon ('98 S70 with 160,000 km). I looked for it when changing oil and coolant a month or so ago, but couldn't find the check plug. Also I only had front ramps and car was not level so I couldn't do the check even if I'd found the plug. It seems it must be annoying to reach because the drain and the fill plugs certainly were not in an easily-seen and easily-accessible place at least under ramps (maybe they are further back than I thought).

I'd buy the MTF from Volvo dealer... that way you can't make it worse! It's probably expensive but you don't need much and the cost over 5 years or so will be minimal.

I've changed the fluid in my S70.

I tried Valvoline synthetic gear oil, and the shift quality was horrendous.

Then I went to Redline MTL, and the shift quality was about the same as the original fluid.

When I changed the fluid in my other car, an old Mazda RX-7, I bought Redline MT-90. On a whim, I decided to try it in my S70, too, and it seemed to yield slightly better shift quality than the MTL did.

--
Jim Rothe, '99 S70 T5M,
http://www.jimrothe.com/volvo/index.html

My Volvo shop sez don't bother.

They indicate that they're likely to introduce more junk into the transmision than they're likely to drain out.

Acura recommends a MT oil change around 120k miles.

I've done a MT oil chanage on my old Porsche (Redline) and it still shifts like a broomstick in a bucket of walnuts.

"Ya pays yer money and ya takes yer choice"

-BTC