I have an Echo CS 451 VL chainsaw; factory specifies 20:1 ratio. While ordering parts at the local dealer I asked the Echo factory Rep. what ratio to use with Echo 50:1 oil. Rep. said to mix @ 50:1. I know the newer oils are better, but I don't want to find out that 50:1 is too lean. I've always used 2 cycle oil in qts. from the auto parts store (I think the factory spec. is for "quality 2 cycle oil") with the best gas I could buy at the pump & have had good results. Saw has had normal maintainance only, & cuts 8 to 10 ricks firewood (oak & hickory) per year. Your experience with this & any thoughts would be appreciated.