Like the other blenders mention...no "little engine fuel" is readily available nearby. I blend high nitro, low synthetic oil fuel, with lower nitro, low synthetic oil, and castor oil. The spreadsheet I pointed to allows for the "recipe" to have two fuels of advertised blends (to include ratios of synth to castor in those two fuels), and castor oil. The results show the resultant numbers for your blend.
My current blend:
Traxxas Top Power Plus 33%N @ 3.5 oz (truggie fuel...I lost the specs, but gleened the numbers from a Traxxas truggie manual)
Wildcat Premium 15% N (Pink Label @ 15% N, 16% oil with oil being 80% synth/20% castor) @ 4 oz
Castor oil @ 1/2 oz
Total yield is 8 ounces that looks, smells, and slimes like old Cox fuel used to. My notes from a few years back indicate the blend to be about 23% N, 19% oil (11% Synth, 8% castor) and 58% methanol (someone check my numbers, please).
Do I expect rocket science-like exact-ness? Nope. However, I bet I'm closer than I really must to be. My price-per-mix is still cheaper than paying for an advertised blend with hazmat fees!
So far, I'm almost out of the Traxxas fuel, have just under 1/2 gallon of the Wildcat, and about out of medicinal grade castor.
No ill effects have been recognized on any of the Cox Reedies, nor the AP .061, nor the Norvels.
As my "version 1" materials are running down, I now have a gallon of straight methanol, a quart of BeNol, and a quart of VPRacing 30% motorsport fuel (9% oil, type unknown). Worst case with the unknown oil is I may have a higher castor content relative to synth. But I'll research carefully before the first blend.