With the high quality valve train components used in bikes and car engines I don't buy into upper cylinder lubes and the hassle of dosing every tank these days .
I do buy into a good dose of Chevron's Techron or similar being used every so often to help clean the back side of the valves and combustion chamber during the last tank of fuel before an oil change .
Even the GM engines are going 300k and more w/o need of a valve job and most of the combustion chambers look pretty clean considering the miles .
Just my opinion based on the many engine tear downs I still see at the local race and machine shops .