I have been running Cool Power 10% in my engines ever since I have owned them. On my last trip to the LHS, I inadvertently purchased Cool Power 15% instead of 10%.

Can I just switch to the 15% and be ok? I know that when you switch brands of fuel, you are suppose to re-break in the engine, but I'm not sure about switching just the nitro content of the same brand.

I have been thinking about upping the nitro content anyways, so I suppose now is as good a time as any.

Thanks for the input!

i wouldn't rebreak it, but i would make sure the needle valve is right for the new fuel

There's no need to re-break in the engine when changing brands of fuel, or nitro content. Fuel it up, tune it, and go fly.
Dennis-

The only difference is it cost more for the 15% but that's my opinion.

I agree with DB. When changing fuel brands and or nitro % the only thing needed is a retune of the needles.

DEG

Thanks for the advice!

Hmmm, my matter of thinking was to LOWER my nitro content as the engine ages/breaks-in. I would think the higher nitro would be required more for a new engine than one that has been broken-in and tuned to the nth degree...

I have a Saito and TT four strokes that I run Mach 7 fuel in (15%) and as they got older hoped I would be abole to run 10% in both. I have about 4 tanks on the Saito and I already have a reliable idle at 2500 or so...

Someone tell me if I am going about this all wrong.

Well, lower nitro will result in less heat production and less overall stress on the engine components, so in those respects it would be better for an older engine.

Increasing the nitro content in an older engine might revive the power a bit, but again it may also accelerate wear.
Dennis-

If you ask Will Robinson, who appears to be the Saito expert at RCU (no offense to anyone, OK?) he recommends Omega 15%, period.
That is what I had been using and continue using, and have had no problems with my Saito 72. Great performance

Luis

You could always go out and get a jug of 5% and mix the two. Just don't do it on a humid day. Oops, you live in Florida, you only HAVE humid days. In that case, do it inside in an air conditioned room.