hate to do this..its an oil thread

[hodge1150]

Im just putting together these Nortons, a 19S, an ES2 and a 2 model 18s. Advice from Mike Pemberton (NOC singles specialist) says use straight 50 weight oil. Having met the guy and entrusted him with a fair bit of engine work, I trust his judgement and knowledge.
Question is this...Ive just googled straight 50 oil

Millers is £45 for 5 litres, Rock oil is £20.51. Why the difference, can someone with greater knowledge about oil than I please offer wisdom

 

[nick.ct]

Check for high or low detergent content...................

You can run a high detergent oil on a rebuilt engine but if you do so on an old motor you run the risk of dislodging all the solids that have stuck themselves harmlessly out of the way and bring them back into circulation to block up the finer oilways, with predictable results.

So, IMHO
Newly rebuilt motors, high detergent single grade eg. http://www.opieoils.co.uk/p-800-silkolene-hardwick-classicvintage-sae-50-monograde-oil.aspx
Old motors, low detergent single grade eg. http://www.opieoils.co.uk/p-808-silkolene-osmaston-sae-50-classicvintage-oil.aspx

 

[Bendy toy]

High detergent keeps fine crud in suspension for the (non-existent) paper filter to catch. Less than ideal unless it's changed very regularly.

Low detergent allows sludge to settle in sump strainer or oil tank. Perfect for old bikes and cars

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