Two U.S. congressmen have asked the Government Accountability Office to study the impact of boosting the amount of ethanol that is blended into U.S. gasoline supplies following a U.S. Environmental Protection Agency statement that it may approve next summer an industry proposal to increase the volume of ethanol in gasoline by 50%—by going from 10% to 15% ethanol (E15).

Representatives Joe Barton of Texas and Greg Walden of Oregon, both Republicans who requested the GAO study, said there are concerns that automakers’ warranties may be voided if gasoline with more than 10% ethanol is used and that higher ethanol blends could also damage engines in lawnmowers, boats, chain saws and small tractors.