I have an easy to start Stihl chainsaw that will start but will not come up to speed. When I do try it dies.

I'm using their Motomix fuel. This is in their information: There are several things you can check. First, make sure that you are using fresh fuel mix (never store or use fuel mix older than 60 days in can or fuel tank)

I'm confused about the store fuel mix in the can. It comes in a can and it saws it's good for two years once opened. Since I use it very little should I purchase qt cans instead of a gallon.

This saw has been to the shop and allegedly runs fine. After the holiday I'm going to take it back and have them show me that it runs fine. Can't figure out what I'm doing wrong.