I had my dealer do the same crap to me and I believed him and I ended up wasting $50 for 5 gallons of U4. They claimed it was oxyginated and MUCH better than C12 which is all I run. So, I gave it a shot and it totally screwed my jetting up. So, I tried to adjust around it and never was able to get it right. Anyway, I'm back to C12 and just recovering from the jetting issues, but still trying to work them out. Anyway, stick to what works for you. In my oppinion, I have not had anything better than C12.