Re: Hypermiling in a Diesel
2.9 l/100km is better considering it was a Passat, not a Golf.
Is your turbocharger equipped with a variable inlet? These are susceptible to a condition we call "surge" in which the pressures produced during full accelerator pedal application, and the relatively slow reaction of the variable vane control at that low an engine speed, can cause turbo damage. Don't try to floor the accelerator at such slow engine speeds for long duration high load use. Shift down a gear or two to accelerate from 1200 or 1400 rpm in 5th or 6th. In 1st, or even 3rd, gear the car will accelerate quickly enough that you won't be at the low rpm and high load condition for long, but leaving the car in 6th at 1400 rpm and driving up a hill with your foot on the floor isn't good.
72 kph will require 44% more power due to air resistance than 60 kph. I don't think that engine operation at 1250 rpm will be 44% more efficient (liters per 100 km) than 1400 rpm.
It will be thermally more efficient as the engine will be at nearer to 100% of it's capability at 1250 rpm and pushing 44% harder, than at a lesser percent of what is likely a higher power capacity at 1400 rpm. From a grams of fuel burned per KwH produced reference the faster road speed and slower engine speed is more efficient.
Is it possible to drive at 1100 rpm in 6th at 65 kph? That would be more efficient in both specific heat energy produced per unit of fuel, and also in distance traveled per unit of fuel.