I recently discovered Repsol transmission oil, it's a 10-30w. It's a lot cheaper than Elf HTX which I had been using. I don't get any drag and the clunk between 4th and 5th on my Pro is LOTS quieter! A couple of my mates are using it now, one has a 315 Mont the other a Sherco and they both say their clutches and gearboxes have never worked better. I got it from BVM in Stroud.