I'm running 10% sport fuel in everything... (usually PowerMaster green)

As long as the oil content is adequate for the engine... this will USUALLY work. Some of the Heli engines will specify that you need more than the typical 18% oil content of general purpose sport model fuel.

The O.S. 4-stroke I have specifies 16% oil... so 18% isn't going to hurt it. It also specifies 10% to 20% nitro recommended. (it seems to run best when I mix 10% and 15% nitro fuel equally. I get 15% when the LHS is out of 10%.)

The O.S. .32 SX-H I have specifies 10% to 30% nitro and 18% oil. (sounds just like what I use...)

You won't find many engines that specify a NEED for more than 10% nitro. And it the engien doesn't need it... there's not any compelling reason to get the higher nitro fuel.

The "Heli fuel" an "Car fuel" labels are just excuses to charge more as far as I have been able to tell. I've tried some and the engines run the same with the same nitro content of "sport" fuel.

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For some forms of competition... the increased nitro will let you burn the fuel faster and effectively advance the engine's timing... that CAN mean youre car can go faster... but usually, just keeping it on the track and upright will do you more good than increasing the nitro.