ive always used duckhams hypergrade oil for my tuned let and it was as quiet as a mouse compared to other xes/ lets. after finding out i can get vaux fully synth for a tenner (mates rates) i decided to use this. (5-40) after putting it in, ive noticed a rattly tappet for about 5 mins after cold start, it never used to do this, also it gennerally sounds a bit rattly. it uses no oil atall, there is no smoke, and uses no water so mechanically it must be mint! am i worrying about ***k all? i just dont want excess wear to the thin oil! or is it better? is it natural for it to rattle with the thinner oil?