Gear oil life

[Phil C]

Morning all, How often should we replace our gear oil? What if we've done very few miles since we last changed it, but that was, say, two years ago? And if we decide to change it, and we reach for the bottle of EP90 which we partly used last time? What's the difference between the oil sitting room in the bottle and the oil sitting in the gear box? Or do we need to buy a new bottle, ie does it have a shelf life once opened?  Phil

[Bess]

Hi,
    Once the gearbox has been flushed from a rebuild its there for life, just top up. Some say 50,000 miles unless stated otherwise in the service schedule. Oils in bottles are okay if the stopper is secure.

Not sure what gearbox you have, be aware EP oils degrade bushes:

https://www.machinerylubrication.com/Read/28958/ep-additives-effects

Best wishes...

[Phil C]

1965 B40F. Do I need to change to something else?  Phil

[Bess]

Hi Phil,
          I had a quick check in the parts manual and it looks like you have bushes in the gearbox. Many use this which is non EP:

https://www.morrislubricantsonline.co.uk/golden-film-ag-90-gear-oil.html

Best wishes...

[Phil C]

Thanks, Bess.
I notice in my owners' handbook/instruction manual, or whatever the little booklet is called (lost the cover), the recommended lubricants for the gearbox are the same as the ones for the engine ( although summer different from winter.) I also notice that Paul Greenfield, in his Feb 2019 article in The Star, entitled "The BSA B40, Chapter 5, The oily bits", uses 20w/50 in his gearbox  unless I'm misreading it (not sure what year and exact model his bike is.) So is engine oil okay in the gearbox then?
That would obviously make things simpler.
Also , if I decide to drain the EP90 and replace with something else, do I need to flush it, and if so how?
Thanks everyone in advance.   Phil.
PS I have a vague feeling we've had this discussion, or something very similar, in the past.

[Greenfield]

Yes that's correct. C15 and B40 gearbox oil is the same as in the engine, 20/50 or 40, whatever you use. My B40 left the factory in '62 and was registered in '63. I think 90EP was used in B50s. I wouldn't bother flushing, unless there's lots of crud in it, just leave it to drain overnight.
Cheers
Paul Greenfield

[Dean Southall]

This is the advantage pf pre war Beezers. The oil's never in the engine or gearbox for long enough to need changing. You just keep topping it up

[Phil C]

So just as I was deciding to put 20w/50 in the gearbox, I noticed this in Rupert Ratio (vol. 1, p.42): " Up until the introduction of sidepoints models, the grade of gearbox oil specified by BSA was the same as engine oil; SAE 30 or 40, or multigrade, depending on which manual was read. From 1965 onward, and the introduction of sidepoints models, the recommended oil was EP90, which is proper gear oil and much better in this application than engine oil."
As I think I've said before, nothing is simple!    Phil

[Phil C]

Btw, mine is 1965 sidepoints. Phil

[DAVE BRADY]

Do not forget that gearboxes can get hot and there can be condensation.  For the sake of a £1 or £2 change the oil after a lay up or before a mad dash around the UK.

Dave.

[Bess]

Hi Phil,
          See attached for oil equivalents.

With the advent of modern oils some went with the oil specifically made for gearboxes, I changed. My A10 specified SAE 50 or 20W/50 and I use the 90 gear oil (non EP). My A65 specified hypoid EP90, I use 90 gear oil (non EP).

For me its all down to reading the handbook, making a judgment around new technology and personnel preference. If you're interested in oils, 'which oil' by Richard Michell is a good read, better than most forums which come up will some bizarre choices and interesting debates.

Don't worry about condensation in the gearbox there are no combustion by-products to contend with. If it does happen it's because water has gotten in will be self evident by emulsification, if water can get in oil can get out.

Best wishes...

[Blackthou]

EP as I'm sure many know means Extreme Pressure and 90 is the viscocity. It was originally only heavy plant or machine-tool gearboxes that had EP.

The thicker the oil, the quieter she runs - to a point, as it doesn't break down as easily. A thin oil in a gearbox would lose its lubricity much more quickly than a heavy oil.

[Phil C]

Thanks everyone. In the end I've ordered some of the 90 non-EP gear oil, as per Bess's link. Difficult choice, as I find so many things in this hobby. Maybe it's an age thing.  Phil

[Blackthou]

I guess you're right re an age thing. It's because you care whereas as nippers anything virtually to hand would do. Oil changes? Never happened, constant top ups yes.

[Greenfield]

A final thought.
I can't find a reference to gearbox lubrication in the sidepoints B40s. Perhaps its in the RR vol2. As far as I know the gearbox was the same until the end of the run, so why should they change the oil grade significantly. The uprated SS90 might be another matter, but only 3hp more. Perhaps someone out there can advise.