My 310R leaky cap story. The original with level switch leaked. Replaced the cap with another, still leaked. Removed some fluid so it was just above the minimum and the dash light occasionally flashing, stopped the leak but not totally happy to take it on track with the light flashing under acceleration. Took 7WotW's advice and put a smear of RRG on the rubber seal, filled fluid to normal level and bingo, no leaks even on track. I think the RRG creates a better seal but also stops the rubber seal creasing as the cap tightens down on to it.