So far I have run YS 53, 63 91 and just starting on a 120NC. The first three have been run extensively with very minor adjustments to any of the mixture settings. My 63 is approaching 4 gallons of fuel with zero maintenance and only adjusted the high speed mix when I flew it on January 1st (25ish degrees) this year and last, then back when it warmed back up I NEED to check the valve adjustment. It is starting to start a little hard and the idle mixture/speed is starting to vary a bit so it has to warm up a bit longer to run correctly. I suspect it needs a new diaphram which I have on hand.
I guess what I'm saying is use the 140. The YS's are a little different but once set up they rarely change and if they do change they usually give you a warning that some maintenance is needed. As far as fuel is concerned I burn Sig 2C 15% nitro. This is a 50:50 mix of castor and synthetic oil. Yes you will have a little more carbon to deal with but I'm happy. IMO any "GOOD" fuel is suitable as long as you have at least 18% oil. 20% is better if full synthetic.
Ken
PS, I think I just started a fuel war thread. LOL You will get many opinions on what fuel to use. If in doubt, follow the YS manual.