Oh oh...here's a can of worms . The best fuel for your LA will have about 22% all castor because of the plain bearing. "Best" in this case means getting the maximum possible life out of the bushing which would likely be far longer than you'll ever use the engine, maybe a couple of piston/liner sets. A blend of synthetic and castor will work ok but the more castor the better. This same fuel will work fine in your ABC engine as well if you only want to have one fuel container or go by what bigedmustafa said as regards oil.

Nitro isn't necessary and both engines will work fine without it. It's got some advantages though, mainly making the needles easier to set and be a bit more forgiving if you don't set them just right but at the expense of higher fuel consumption (shorter flights) and more expensive fuel. If you need nitro for the small amount of extra power it gives then it means your engine isn't matched to the plane (flame suit on ).