Silkolene Comp 2 Pre-Mix Engine Oil ?

Hi James,

Most of the oils originally recommended by Norton Motors at the end of the '80s are no longer available.

Low ash, so nothing left after burn to stick seals in seal grooves.

No additives, so no sticky residues to stick seals in grooves.

Absolutely nothing multigrade.

And probably formulated for 2 stroke diesels of the era. Rare then and in marine use, perhaps.

I know only of the Silkolene product you mention above, favoured by many, and Shell Rotella DD+ 40 favoured by the rest.

The Silkolene is more easily come by, but costs more per litre. The Rotella, and you must get the correct grade, is cheaper but you may have to buy a large drum.

Best information says you can't mix these oils. I have run with Rotella for 25 years which I get through a bulk purchase scheme of the UK based Rotary Owners Club. 25 years ago Shell would deliver 5 gallon drums to my door. Now they only deliver 45 gallon drums to the ROC which members draw on. Not much use for you in the USA.

However, I do believe the Shell Rotella I use comes from Shell in the USA, so perhaps worth a few enquiries on your part.

Have you bought a rotary?

Peter Holland

I worked at Shenstone as a development engineer, mostly on air cooled rotary engine durability. We always used Rotella but I don't know the history as to why it was chosen or what viscosity it was. The RAF ran some rotaries and they wanted to know if they could use MOD spec oil so one of my tasks was to run an engine on the test bed with their oil. When I stripped it down it was obvious that it wasn't suitable, the inside of the engine was covered in black soot, a bit like burnt treacle. If I owned a rotary I would go out of my way to get some Rotella. I have no experience of running them on modern 2 stroke oils so I can't comment on that.

Brian Peers

Many years ago I had a rotary and wondered about which oil to use.   I asked a Fuchs (Silkolene) guy at one of the big bike shows.  He recommended a high ash content oil.  This seemed an odd choice to me.  I used it, seemed okay on it but I didn't keep the bike for very long.

Many years ago I was involved in some testing of the rotary, specifically measuring the mechanical losses within the engine.  I recall seeing cans of Silkolene 2 stoke next to the test rig but cannot recall what grade, should have paid more attention!