I'll bet you that my running the higher nitro with more power but running cooler will last longer then your lower powered hot running engine. heat is the death of an engine not RPM (within the Recommended Range). I've got an OS 70 surpass that swings a 10x10 APC at just over 10 grand with the 30% fuel, it's 7+ yrs old and runs just as good today as it did when it was new, it's still all original and has only had the valves adjusted once after initial break-in. my flying partner has a Saito 45 that never misses a tic and been running 30% for i know the past 10 yrs (the engine is conciderably older then that but ran 15% prior to the 30%)

understand that Nitro is one of the few things in life (just mentioned this in another post about the same subject the other day) that IS a 'Win Win' situation. not only is it a power boosting product it's also a cooling agent. in all other instances of engines more power means more heat, this is not the case with nitro. you can however get to a to high a percentage and get pre-ignition which is detrimental to an engine as it over stresses the con-rod but this isn't the case in any of the 4-strokes running 30% and only a very few cases with 2 stroke applications (heli's and ducted fans) but these few cases can be cured by adding a head shim to lower compression.

and just for giggles, Castor is not recommended in 4-strokes due to the carbon deposits and build up on the exhaust valve(s) although allot of your 4-stroke fuels are a Castor/Synthetic blend.

kc