Hoping to save cost, I bought a gallon of Tower 0% fuel for the Alpha. The plane didn't idle very good, and forced me to be alert for dead stick situations anytime and all the time. Bought some new 10% mix and it was like putting a new motor in. No more dead sticks and idles so good I can't hardly kill it when I need to.

don't be to quick to blame the fuel!!!

When you use fuel with different % of nitro it is sometimes neccessary to change glow plugs. I was allways told that if you use 0-5% to also get a hoter glow plug.

I know some engines seem to even "like" one brand of fuel of another (brand x and y both claim 15% nitro) yet engines performs better with brand y

Yup, I've noticed even the needle adjustments can change as you switch between nitro content...

my alpha would not run on magnum fuel, but has never had a dead stick (with fuel in tank) on performance plus..and to think about it my O.S. 46 FX did the same...not trying to bad mouth any one but thats what happened to me...spooner

I can get 15% for $15 or so, it makes my planes happy

i got 15% for 11.00US it is magnum. it runs better in my TTpro46 than did Sig 10%

If you try a fuel with a different nitro % then you MUST readjust the needle settings (particularly high speed). Think of it this way, if you decided to run your lawnmower on methanol instead of gas then the carb jets have to be twice as big in area to flow enough methanol. Nitro has the same affect on methanol. The jet has to be bigger than what methanol by itself needs but it's easy for us to make the jet bigger, we just screw the needle out a bit

Actually it's good practise to retune even if you only change brands of fuel.

Ive used the same kind and % since I started 3+ years ago. My first engine still runs.

I'm not surprised that going from 0% to 10% had a huge change. That's a huge jump in nitro, and the changes you noticed are exactly what you should expect. Going from 10% to 15% will show a much smaller change, and unless you're looking for every last RPM, going over 15% is a waste for most guys.

You mentioned changing plugs with nitro. More importantly, engines set up to run on 0% fuel usually have higher compression than engines set up for more nitro. So, if you want to run 0% nitro, you can benifit by removing the head shim or going to a thinner shim. On the flip side, many European imports are set up for 0%, and to get them to run smoothly on American 15%, adding a head shim does wonders. As I understand it, nitro is much more expensive in Europe than in the USA.

Also, differnet brands of fuel do perform differently. Mostly the differences are in the oil % and the types of oils in the fuel.

Lower oil % means higher power, as there is more burnable stuff in there. But some engines like more oil and will actually pick up RPMs if you increase the oil to a certain point. Also, some oils are just better at lubrication than others, so a smaller % of some type of oil will work better than a larger % of another, and leave more burnable fuel, resulting in better performance all around. There's a guy in my club who runs custom fuel with only 10% oil, and he never burns up engines. But he knows his engines, and he doesn't set them lean. I, on the other hand, like the insurance of a bit more oil, but I don't run 20% either. I do like a dash of caster in my fuel though, so I run Morgan Omega, which is roughly 17% or 18% oil, mostly synthetic, but it does have some caster.

To top it off, air temperature and humidity can really affect engine runs as well. And some fuels will perform better than others in different weather. For example, on a high humidity day, you might want more or less oil than on a dry day.

The good news is that 99% of this only matter when you really are pushing engines. Even when I fly competitions, I still run good ole 15% sport fuel just to keep my life simple. I might give up a few hundred RPM, but that's ok for me.

Btw, there is lots of good fuel and engine performance info on the powermaster website. I seem to have lost the url, but they have a FAQ on there that was written by their former owner that is almost a "must read", even if you never buy powermaster fuel.

Some of the guys that I have talked to insist that if you change fuel, even brands of fuel that the engine should be broken in just like a new engine , never had occasion to try this myself ,but they claim that the K+B's and older fox engines were very sensitive to fuel changes, and even some of the new ones are also.

I use wildcat 15% for all my engines .

Highlander