General => Douglas Motorcycles - General Discussion => Topic started by: Biggles1957 on 21 May 2021 at 10:52

Title: Dragonfly gearbox
Post by: Biggles1957 on 21 May 2021 at 10:52
Can someone clarify what is the correct (or best?) oil to use in the Dragonfly gearbox please?  The book says SAE 140 (although I'm not sure if it is meant to me EP or just plain 140) but I've read that some people just use SAE 40 (again not sure if it's EP or not).  The previous owner used classic 20/50 oil in the engine so any advice on that would be appreciated too.  Many thanks.
Title: Re: Dragonfly gearbox
Post by: kncken on 21 May 2021 at 11:49
Hi Biggles. It used to be so,I think,that EP oils were to be avoided in 'boxes which had phosphor-bronze bushes,as is the case of the Dragonfly,Marks and most classic machines,but that is not neccessarily so now,maybe(!?) However,I am currently using ,in my D'fly,Morris's Golden Film AG90 Classic Gear Oil,which they emphatically state is OK with phosphor-bronze .All the best,Ken.
Title: Re: Dragonfly gearbox
Post by: EW-Ron on 21 May 2021 at 22:16
Its perhaps also worth mentioning that engine oil and gearbox oil viscosities are not directly comparable - for a reason.
50 wt engine oil is approx 90 wt gearbox oil (?).
Done so that one is not inadvertantly used in place of another - in the wrong applications.

140 wt oil is quite a heavy gearbox oil, one or two shade below those liquid greases. (?)
It can be purchased as such, although not common.
An old time specification, so its just a plain heavy oil.
(and may not contain all the anti-rust etc additives that make modern oils sooo much better)

Any good modern oil could probably substitute, although it will be thinner.
And possibly leak more, if the oil seals are not to modern standards ?
Not knowing how Dragonflys are so equipped ...