Carmakers disagree however, claiming that anything beyond a ten percent blend could cause problems for cars in the field due to corrosion. The cars tested in the study were relatively new and recent model cars would likely have few, if any, problems running on E20. The issue lies in the fact that with close to 300 million cars on the road in the U.S. now, and a median age of nine and a half years, half of those cars are over a decade old. Most of those cars very likely will have issues with E20. There is also the issue of whether we should be pushing harder for more widespread use of ethanol until cellulosic sources become commercially available. I'll leave that argument for another time. None of this however is likely to stymie any politician promoting the products of his state.
[Source: USA Today, Via The Truth About Cars]