Averaged 3.3L/100km (85 MPG UK or 71 MPG US) over the last 975km (605mi) on a single fill. Fuel reserve is not even on yet.
2010 Peugeot 107 1.4HDi 55PS 965kg.
The result of a small diesel city-car and doing moderate hypermilling. This time I filled with 32.27L after 975.8km which equals to a fuel consumption of 3.3L/100km (85 MPG UK or 71 MPG US) and the fuel reserve wasn't even on. By my calculations there was still 6.5L left in the tank so the fuel reserve would have turned on at 1025km (637mi) and I'd have run out of fuel at 1177km (731mi), that's with a 38.5-39L fuel tank (that's how much I fill by my estimations).
My average over the last 3000km is 3.36L/100km (84 MPG UK or 70 MPG US) so just slightly higher. I do mostly highways at 100km/h (62mi/h) but sometimes I take advantage of trucks and go behind them at 90km/h (56mi/h). I use engine brake as much as possible (not as much if I have drivers behind me, I try not to bother people) and low gears. I also made sure the odometer is accurate comparing distances with Google Maps.