Recently, some aircraft sellers have told buyers that certain aircraft can use auto fuel when they're not certified to do this, EAA said last week. A records check failed to confirm that one such aircraft had an autofuel supplementary type certificate (STC), and there were no placards on the aircraft. Only EAA and Peterson Aviation are authorized to issue the autofuel placards. If you are buying an aircraft that you were told has an autofuel STC, EAA recommends that you check to make sure the aircraft does indeed have it. The best way to do that is to look for autofuel placards on the wings next to the fuel inlets, and also contact both STC holders. Petersen Aviation can be contacted via its Web site and EAA can be reached by e-mail, or call 920-426-4843 to see if the records are on file. An autofuel STC can save you a lot of money over the years and can add to the value of your aircraft when you want to sell, says EAA. An autofuel STC can save you a lot of money over the years and can add to the value of your aircraft when you want to sell, says EAA. "There has been a slight uptick on new STC applications recently, which has been brought on by a combination of the threat of new fuel taxes and higher aviation fuel prices in general," EAA spokesman Dick Knapinski told AVweb on Tuesday. "We're seeing an increased interest in including the addition of an autofuel STC prior to the sale.