Gear box oil

[BSAA10]

Am I advised to use a fully mineral gear oil in the old BSA or is a synthetic better.
I am using Castrol VMX 80 at present. Thanks

[Rocket Racer]

The BSA box is a tough old thing, but the layshaft bushes don't like sulphur additives. Other than that its largely personal preference. I like red line synthetic in mine.
Most boxes I've  seen have worn layshaft bearings. These gearboxes can take a lot of abuse. 

[BSAA10]

Thank you. Excuse my ignorance but I thought all GL5 oils had a higher sulpher content. Aren't all Redline synthetics GL5?
Thanks

[Rocket Racer]

Aren't all Redline synthetics GL5?
Thanks

I'm sure many are, but not all. I run on their MTL product. Its certainly given me good service.

[BSAA10]

Thank you.

[Rocket Racer]

Cheers
 As long as its clean and to the right level, these boxes are pretty hardy, sadly they are all also sixty odd years old so wear can be present. I have a decent stock of gearbox spares in serviceable condition if your box ever needs a fresh STD dog. The bushed layshafts are the common point of wear although a box I'm currently setting up has worn sleeve gear bushes which need work and worth doing for a SC box.

[BSAA10]

Thanks again for your input. You obviously have good knowledge, what engine oil do you use? Again, thanks.

[Rocket Racer]

  sounds like I'd better do another plug for the counselling session on the 12th August, Northcote Tavern after 6:30...

I can't be much help to you there, my race engine runs on Morris 40 castor oil and so I can always swap engines if need be, so my road A10 (super rocket project) will also run on it.
So not compatible with any mineral oils I could recommend.

The one thing I would say about engine oils is that firstly do you know much about the history of the build. The A10's run a sludge trap and quietly accumulate the stuff. So unless you have a nice fresh sludge free crank I would recommend a monograde (Morris do a good straight 40) like they ran back in '60. If you have a nice clean motor you can opt to run modern multigrade oils with detergents but should also have a modern return oil filter and a clean oil tank.

A10's must have clean engine oil for long life.
Also recommend cleaning the sump gauze routinely