With the two blends will the car have problems switch back and forth when the car was tunned on one of them or will the car need to be tunned twice for both blends when the time comes to switch?

 

prob will have issues....winter blend here in mn is 70% ethanol and summer is around 85%. that will effect the knock resistance. so you tune on 85% you can prob get a more aggresive tune but when the winter blend comes around....you lose that buffer