Jag hittade nedanstående text på Andover Nortons hemsida:
What oil for a Commando? One should have thought, this is answered by workshop manuals and Riders Handbooks.
Unfortunately, this is not the case, as the oils recommended there are not really suitable.
In production times Nortons first and foremost aim was to sell motorcycles. To do that they recommended not the oils that were technically best, but oils that could be bought at any garage.
This is the only reason why Multigrades were recommended. Friends from within the Lubricant industry, as well as Richard Negus, ex-Norton Motors "Chief of Motorcycles, and ex-owner & tuner of the most successful long distance racing Commandos, both confirm that, with the high temperatures combined with the high pressures in a roller-bearing engine, multigrade additives give up quickly and leave you with the base oil within as little as 600 miles- which means you 20W50 becomes 20 oil, which is not up to the job in a Commando engine used propperly!
As for the primary drive, oils have changed dramatically since the early seventies, and additives we used to put into our engine oil, like STP, are now already contained in most multigrade oils. These additives are molybdenum (graphite) based, and will give you clutch slip very quickly.
Therefore, we recommend:
Engine
Straight 40 oil
Primary
Either a Monograde oil, or (better) ATF oil; I use Shell Donax TX
Gearbox
EP90 gearbox oil
