I've been using a mineral to run in ,Silkolene Superma 15w-50 .
It seems to be doing the job just fine and is a third the price of the Pro S .
Pressure is always fine , 3 to 4 on tickover and max at all other times .
I think'll continue using it for a while and see how it goes .The spec sheet looks pretty close to the expensive stuffs blurb .................and thats designed for very serious motors , maybe it's overkilll on the GTA
How can you gauge an oils performance in the real world ???? ie no textbook quotations/engine rebuilds
Can I tell by the colour/smell when I bin it 
