New to this forum. Several fuel additive products claim to contain lubricants for the engines "top end", as a replacement for the lubricating qualities of lead no longer found in unleaded fuels. (Several of my friends run a 50:50 mix of pump gas/leaded race gas in their dirt bikes, just for this reason.)
In particular, Redline Complete Fuel System Cleaner and Klotz Octane Booster. I have run the Redline product in my truck fuel (and Redline oil in the crank case) and the Klotz product in my quads fuel (and Maxima Extra or Ultra oil in the crank case).
I presume both these products contain some kind of ester synthetic for the top end lubrication, as both these brands are big on esters (???).