I have  a  friend in the   Oil  refinery business  ---  a chemist,  and he says  that  there is  nothing  bad with this new gas... the problem is the old tractor  sits longer  than  they use to -0--- and  with the  additives the gas has---  ( for anti knock,  water retention,  cleaning injectors and the like)   these help stick  or gum  up  stuff when  they sit to long---  he  has  antique tractors too and  says  just  run them once in a while  and you will not be  sorry.