I did some research on the fuels normally stocked at my LHS's.  They carry Omega, Cool Power and a few other brands, along with Wildcat. Of all of them, Wildcat was the only one that comes with 18-20% oil content. Its full synthetic except for the 20% Heli blend.  I have been using that stuff now and have gone through 3 gallons along with my friends using 4, and not a single problem out of 5 different engines of different displacements using  the 15%N/18% oil mix. It is also a couple buck less expensive.

Both my Magnums recommend 15% Nitro with at least 18% oil content, Castor blend recommended for break in, but the Wildcat worked fine for that, and I am pretty sure they use Klotz oil.  If you can find Wildcat, you can't go wrong with it. I get it for about $16 a gallon.