Engine oil

[sidewaysid]

My 1947 B31 is now getting to the stage where I need to try to fire her up, and engine oil is a question, I would like to start with an oil that I stay with, I have looked at the Silkolene range, I was sure the 30s oil was for me, but now I am uncertain, the 40s and the 50s straight oils seem very much the same? any advice on the matter.

[idie]

I run my M33 and B33 on straight 40 grade have done for years.

[Pete Gill]

Hi there,
This is the page from the B series handbook.
I'm getting to the same place considering oil to use. I've added a filter in the return line and I think I'll use 20w/50 multigrade.

Pete

[Pete C]

ditto...I buy straight 50 and 30 no detergent oil in canisters and mix 1:1. Then if it is a very cold winter or a hot summer I have the option to alter the oil to suit. BSA quote 30 for winter and 50 for summer but 40 is OK all year as long normally.

The main thing is to have clean oil, so change frequently, which means no expensive oil otherwise there is the temptation to delay changes. There is practically no filtration on these bikes so any rubbish is only going to stop ciculating when you do an oil change.

[Pete C]

there are more knowledgeable people out there than me ..but.. I seem to remember reading that multigrades are not really all that good for engines with a lot of roller bearings- like ours. 

Apparently the multigrade properties result from long chain molecules that alter their structure depending on the temperature and so provide the same viscosity over a range of temperatures. This OK in an engine with plain bearings but the rollers tend to degrade these chains (chop them up ) and you end up with oil that has lost much of its "multigrade" properties.  Straight grade oils don't have these chains so rollers don't affect them.

Could be a load of rubbish but I read it on the internet so it must be true. 

[idie]

When Duckham 20-50 came out the Duckhams rep told me just that and to keep to straight oil.

[B Murphy]

Run my B31 on straight 40, no problem. This oil question is always going to be a can of worms it's on every forum with loads of different answers  . Best to do your own investigation........then come back and tell us your findings 

[maddogmargetts@yahoo.co.u]

thats interesting, i run my M21 on 20/50 Halfords classic oil that does not have detergents but I never knew about the other stuff about it degrading and mashing up bearings. I wonder where you get straight 40 oil? Have never seen that in the usual shops

[Pete A10]

Have a look at alexoils.co.uk. They do a range of oils called Lubron which includes Classic engine oil, non detergent, in sae 40, 30 and 20. Comes in 5l or 1l containers. I've used it in my B40 and A10 with no problems - just change it regularly as it doesn't last for ever.

[martinh10]

I use Castrol Classic XXL40 in my B31. It's fairly widely available but I order it from my local bike shop (Shorrocks) who get it within a day or two. Castrol say it's for:
"pre-1950 cars and pre-1970 motorcycles. High quality monograde engine oil recommended for single and multi-cylinder engines under road and competition conditions."
It comes in a nice steel one gallon can as well if you like that kind of thing.

[B Murphy]

thats interesting, i run my M21 on 20/50 Halfords classic oil that does not have detergents but I never knew about the other stuff about it degrading and mashing up bearings. I wonder where you get straight 40 oil? Have never seen that in the usual shops

This is what I use -

Full Product Description:

SAE40 Classic Motor Oil is a specialist lubricant designed for use in veteran, vintage and classic motor vehicles & motorcycles. The high-quality, low detergent monograde mineral lubricants are suitable for use in naturally aspirated 4 stroke petrol and diesel engines and manual operated gearboxes of that age, providing maximum protection to prolong the life performance of treasured classics.