I was recomended 10w60 by a local engineering/car tuning firm for my cossie, on trusting there judement and filling the engine with this I started the car on a cold morning and heard what I can only describe as a loud thudding from the bottom end, the big ends ?

OIL WAS REMOVED IMEDIATELY, (now using mobil 1 10w50) and research carried out and came up with same answer as oilman