The oil is the difference. A lot of 'heli' fuels have 22-24% oil. Many 'airplane' fuels have 16-20%. 'Car' fuel often has 8-14%.

The Saito manual says their "benchmark" numbers were obtained using Powermaster two stroke fuel with 15% nitro. They recommend 20% oil content, but some of the fuel brands they list as 'recommended' only have 17% or 18%.

I think a lot of people who use 30% nitro go for the higher oil content hoping it will make the engine last longer.