I have mixed my own fuel for many years with success. Mainly because I like to run big glow engines (moki / Mark 180 or 210). these are 30 or 35 cc glow engines and will burn over 2 ounces per minute. they run fine on 0 percent fuel, although I usually mix up 5% nitro. The small glow engines (e.g. OS .46) will also run on 5% but not as nice as 15%. For the big glow engines I can run a little less oil (15% instead of 18 or 20%) which also keeps the cost down. Oil and Nitro are the expensive bits in the mix.