On the subject of fuel economy, on a Northern outpost many years ago we discovered that the Sherpa in second gear would rive at a respectable walking speed with your feet off the pedals, and the speed could be controlled by using the manual choke. This worked well on guard shifts until the MTO phoned the guard chief to ask why this particular Sherpa needed filled twice a night?
As for non-faults, I remember a trip to Gibralter when we ferried a spare ECM pod on another wing station. On landing there was almost fisticuffs when the Nav insisted he snag it because he "could not get that second ECM pod to time out" but would not accept that it wasn't even connected!
P.S. the sunspot activity charts in the back of the on-route supplement could be used to convince Navs that the poor HF performance was due to cosmic radiation, not the fact that the radios were out of the ark!