In a letter delivered to the White House and signed by more than 300 trucking executives, the executives have told President Bush that they will not buy trucks equipped with reduced-emission diesel engines required by interim 2004 Environmental Protection Agency regulations, according to the National Association of Fleet Administrators (NAFA).According to the executives, the new engines have not yet been proven reliable for day-to-day operations. In the letter, the executives stated, "With less than four months before the October effective date, there is no time left for us to thoroughly test the engines. In fact, most of the fleets do not yet have access to the new engines. To date, only one company has an EPA-certified engine that meets the new standard and that company has only a handful of engines out for field testing."Some fleets have rushed orders for current product to beat the deadline for new engines. Some fleets voiced concern over reliability, while others object to higher initial costs and reduced fuel economy reported about the new engines.