I just bought a new toy (gas trimmer) that requires a 40:1 gas to oil ratio. All of my other tools use a 50:1 mix and it's always pretty fresh cause I use it a lot. I won't be using this new toy a whole lot and didn't want to mix up a separate batch that would just go bad over time. So I made up a chart indicating how many drops of oil I need to add to my 50:1 mix to get a 40:1 mix. I'll be using just 8 ounces of gas at a time, so according to the below chart, if I start with 8 ounces of my 50:1 mix and add 26 drops of oil, I'll have a 40:1 mix. Basically, just add 3.25 drops of oil for each ounce of 50:1 gas. Don't worry about the fractions of a drop. Just round things off. Using an eye dropper is the easiest way to do this. Thought this might be helpful to others.
OK. OK. I just retired and have wwwaaayyy to much time on my hands ! ! !