Morning all.
I have a 1965 SS80, all the books and charts that I have advocate sae40 and 30 for the engine summer and winter respectively.
Did BSA ever advocate sae 20-50 please?
I was thinking of speed of oil flow when cold really, but I am aware that the SS80 has a roller big end.
Thank you for any thoughts.
I think the issue is more to do with oil filters and detergent. AFAIK .. 20-50 oils are all detergent oils designed to hold the rubbish in suspension, so that it can be captured by the oil filter. Old BSAs generally don't have a proper oil filter - just a token gauze. So therefore you need a monograde oil, which are normally non-detergent. These allow the crud to collect in harmless corners of the engine. I have fitted a screw-on Citroen 2CV oil filter rig to my RoyalStar500, so I run that on 20/50. Whilst my C15 will be run on straight 40 (I don't ride in winter).
Hi,
Don't forget that there is a sludge trap in most engines so sludge accumulates there as well as in odd corners of the engine.
Some 'classic' 20-50s may be detergent free or low detergent.
The obstruction of oil flow due to blocked sludge traps causes problems from elevated wear rate to catastrophic failure.
I believe that the sludge trap on the unit single is rather small whereas in the twins it is quite cavernous in comparison.
I would suggest a filter on all engines as it will trap any other particles that could be harmful if left circulating but the filter may offer some resistance to cold mono-grade oils so the 20-50 seems still to be an option.
Dave.
Thank you for these thoughts.
I confess to not thi King about the detergent aspect as I change my oils very regularly as lower mileage now.
But I think I'll leave the bike on 40 or change to 30 as I ride all year.
Cheers
"Castrol Classic Oils are specially formulated in the style of the original products. Using traditional mineral oil and a low detergent formulation, Castrol Classic Oils are the right choice for your cherished classic or vintage vehicle".
https://www.classicoils.co.uk/engine (https://www.classicoils.co.uk/engine)
"Morris Golden Film SAE 20W-50 Classic Motor Oil is specialist high quality, low detergent/dispersant multigrade lubricant".
https://www.morrislubricants.co.uk/products/classsteam/classic-engine-oils/golden-film-20w-50-classic-motor-oil.html (https://www.morrislubricants.co.uk/products/classsteam/classic-engine-oils/golden-film-20w-50-classic-motor-oil.html)
Useful to know of this brand, cheers