Rover P4 80 I am going to change the gearbox & overdrive oil, but there seems to be a bit of confusion about which oil to use, the manuals say EP90 but some members say 20w 50 engine oil, what do members think or what have they used when doing a gearbox oil change, I also have a slight gearbox oil leak dripping from the bell housing so thinking of adding some stop leak to the refill oil so the thicker oil may be best ie - EP90