I can tell you from first hand experience. I rebuilt the 600 Edelbrock on my 69 Dart because it was not running good, ( turned out to be from Ethanol in my gas). the inside of my carb looked nasty. None the less I soaked it rebuilt it and was running good again. After driving it to a car show I put it back in the garage and time got away from me and it sat three months before I went to drive it again. Well it ran like crap again so i pulled the carb off,took it apart and I couldn't believe that I just had rebuilt it 3 months prior to this! It was full of corrosion and crap, it looked like it had been sitting for 10 years not three months! That was it, done with ethanol/gas mix. Now I run only Ethanol free and have not had another problem. This is my experience with 10% ethanol.