Kemper use the oil equal to MF 1127. I was told that thicker oil would some how shear some thing in the drivetrian of the internal oil pump in colder temperatures.
Its more a case of what you dont use. DO NOT use a extreme pressure type oil - the smelly stuff you would normally put in a truck rear end - this type oil will eat up the brass synchro rings and etc in the massey manual gearbox. We use a detroit deisel 50 grade engine oil, but there would be lots of other suitable choices. Cheers Greyhawk