At what speeds and altitudes is the 270 rang at? On the first leg of the Dempster your typically 45-60mph and at elevations 2-4k. The EFI will lean your engine out as necessary depending on barometric pressure and altitude compensation. At sea level to 2k ft and 70-80mph i typically get 180mi out of 4gal. On that leg of the Dempster I made it into Eagle Plans without using my reserve fuel.