I think with oils a lot of its down to personal choice,ive been using millers motorsport 10/60.

Ive just ordered some silkolene Pro-R 15/50 (20 litres)!! and i came on here and found people were saying its no good and it makes the engine sound foooked!! GUTTED.

I was told it was told by a very reputable source that the mobil 15/50 and the silkolene 15/50 are the best oils to use,soill give it a change and see how it goes.