I just picked up a Tower .46 on the cheap. I am running 20%/20% in my OS 46 AX. I was trying to stretch every bit out of the OS trying to pull a UCD 46. Since then I have changed to a Katana profile and the AX is strong enough for that.

The question is... The Tower 46 specs 15% nitro maximum. Can I run the 20/20 in it or is the 15% critical? I don't want to keep 2 fuels around.

Thanks in advance.

That will work, just richen it up a tad so you don't burn plugs out.

At some point with a nitro overdose you'll likely encounter pre-detonation. If you start noticing thrown props and broken connector rods you might want to back off.

You could mix a little of the 20% into every gallon of 15% and use it up that way or you could buy a gallon of 10% and mix equal portions.

You won't notice the difference between 15 and 20% nitro fuels.

Thanks for the replies.

HighPlains - So I won't notice the difference or the engine won't know the difference.

Unless I hear different I think I will run her rich and see what happens this afternoon. I am not out much of anything if something goes wrong unless it throws the prop through my neck.[]

There is very little difference in engine performance between 15 and 20% fuels - maybe 100 rpm or so. The needle setting on your engine will be more affected by variations in conditions than this minor fuel change. I've run fuels with nitro ranging from 5% to 70% for over 40 years, and except for a few engines that are set up for FAI type fuels, most model engines are pretty tollerent of minor variations in nitro content. Oil content is a different matter, and having the right prop and needle setting is most important to keeping an engine running well.

That and avoiding dirt.

15% is what the engine will take with current comp ratio. To increase the Nitro content of the fuel you would have to use another head shim.

Cheers