Any grade of oil leaks out of the gearbox quite quickly. I have stripped gearboxes in which grease has been used and the gears run almost completely un-lubricated in clear channels between solid walls of grease. Some people uses a mixture of oil and grease but the best material I have found is called semi fluid grease. I was given a small flask of this some years ago and have found it to be excellent. Leakage is negligible but because it creeps and is self levelling the gears are always well lubricated. My flask has lost its label so I do not know what grade it is. It comes in three grades, 0, 00 and 000. It very difficult to get hold of in reasonable quantities. It is used extensively in agricultural machinery and Internet searches show that suppliers are few and far between and they like to sell it in drums. A contact in the London Douglas Club recently found a source in Southampton in the South of England in a do-it-yourself size container but it was the 000 grade and that was much too thin and leaked almost as badly as oil so I think it must be the 0 grade that I have (mine is red and came from the USA) but my supply is almost exhausted so I am actively seeking a new source.
