The oils are manufactured to work properly at a given ratio. Some oils, such as Amsoil, I believe are made to run at 100:1 ratio. Many, like the Husky oil run at 50:1. Others run in the 40:1 ratio.
I was taught by pro motocross racer and mechanic to mix by what the oil company recomends. If you run it leaner than recomended, it will not lubricate enough. If you run it richer than specced, it gets too much oil in the comustion chamber. That will foul the plug, affect performance, and make a lot of smoke. It can also cause the engine to run hotter, as the oil tried to burn in the combustion chamber.
Many engine manufacturers will spec an oil and a ratio. If you change oils, it is not necessarily best to remain with the engine spec ratio. Different oils have differing viscosities and lubricating values.
I had an old boat with a 75hp outboard a few years back. Got it for $300. It ran terrible, and fouled plugs constantly. We took over 50 plugs out of the storage cubbies; they were all fouled. Knew folks who went fishing with the guy; after about 1/2 hour of use, he had to change plugs...
I cleaned the gas tank and fuel system up. Put new plugs in it... Then I filled it up with Pennzoil outboard oil and fresh gas(same oil the guy had used). It ran great for the next two years I had it. Well, I ran it at 50:1, which is what the oil was designed for. He had been running it at 20:1, like an 1960's manual for the motor said to do. That 20:1 was fouling the plugs like crazy. The 50:1, properly mixed per oil company spec, worked great. I never changed another plug on that motor, and it ran great!
He was using a spec for a different oil that wasn't even made anymore.
Since I started running oil by the oil maker spec, like Steve told me too, I have never had an issue with a 2-stroke motor. The plugs have been clean and the engine hardly smoked at all.
I did lose a dirt bike engine to bad oil once. Roasted the rings and cylinder wall on my old Honda CR450. Found out the oil company had a bad batch get out to the public. A few people lost motors... I can't remember what oil it was; it was 15 years ago. I switched at that time to Hi-Point racing oil, and never had another dirt bike problem...
I use those Husky "6-packs" too, for one gallon mixes. They work great.
I only mix 1 gallon at a time, and try to use it up promptly. Another thing my buddy Steve the motocross racer taught/told me, was that once you mix the oil and gas, the oil starts to break down. If your not using it within a couple days, dispose of it. Many people think that is a joke. But, for him, that fresh gas could mean the difference between winning or losin the big race. For you or me, it probably doesn't hurt to let it sit. But, why risk the investment in you power tool?
So ends my Friday afternoon novel/w3tcompact/icons/grin.gif