Normally service my own bike but this time it needed valve clearances so I booked it in somewhere I trusted and they offered me this as an extra as I ride all year round.
This stuff is meant to make the oil 'stick' to the components of the head and throughout the smaller oil channels better so the engine is protected at start up from cold and is meant to stop the oil thinning so much when hot.
All I can tell you is that the top end was a bit rattly going in, and when I picked the bike up the engine was smooth and silent. All I could hear was the exhaust starting from cold, and 300 miles later it's still the same.
I recommended this to a friend who was planning a bike trip round Spain as he complained as the bike got hotter the engine rattles of his ageing XJR 1300 got louder and he was worried the top end was being starved of oil due to temperature thinning the oil. He has given me the big thumbs up from Spain and stated the bike is running fine.
I have bought this one for my next interim service at home and have no hesitation using it again.