Navy, it's good stuff mate.
Mostly semi-synthetic, but I hear the 0W20 is full synthetic.
It's quite unique, most semi-synthetics are probably group 2 and group 3 oil. This stuff has an ester (group 5) added to the oil that clings to the metal surfaces and doesn't drain back into the sump when the car is parked overnight. So I think it's some sort of Group 2/3/5 blend. What else gives you group 5 in the mix for that sort of money?
It was talked about here
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3890995/Oil's_Affinity_for_Metal_?#Post3890995
Originally Posted By: Shannow
Had dinner with a former Castrol Chemist, who was involved in some of their testing down here. He no longer works for them, so I see his praise as having some worth.
He was explaining that in their test engines, they use a flushing oil (bugger all additives), followed by the reference oil (Mobil 1 5W-50), followed by a flush, their oil, another flush, the reference oil etc.
He said that during the magnatec testing, the baselines, and the flushes all improved with the residual from the magnatec.
Regards,
Army