ORIGINAL: Capflyboy05
The one I am most interested in running right now is an Enya 45.
VERY old engine.
I'll take a guess that your Enya has either model 6001 or 6002 cast on the side of it. If so then they're quite old, baffled piston with rings and are very good engines. I've only ever run mine with 20-25% all castor and no nitro but I mix my own fuel so you won't find anything like that at the LHS. It'll run fine with some nitro but the oil content might be a bit of a problem because most fuels lately are somewhat lacking in oil, especially castor.
Nitro is an American phenomenon, mainly because nitro is cheap there and it'll give a boost in power, but the truth is that all 2 stroke engines will run perfectly well with zero nitro. 4 strokes will also run on zero nitro but they're designed with very low compression so they can use high nitro fuels to boost their power to come closer to matching the power of a similar sized 2 stroke.
If your other engines are similar to the Enya (ringed with steel liner or even ABC) then the fuel Jim Thomerson mentioned would be fine but if any have a cast iron piston then you're going to need 25% all castor. A list of your engines would help though.