Kiyoshi,


Since the OS will typically be running on higher nitro fuel and possibly have too hot a glow-plug, it will consume more fuel than the ST.

If you change the glow-plug (which might be the super-hot A3. If it is an OS #8, leave it there) in the OS to a medium heat one, like the K&B-1L, Enya #4, Novarossi C6-S, OS #8, or others and use 5% nitro fuel, like the ST will happily use all year long, both engines will, after adjustment, consume fuel in about equal amounts.