I spent most of yesterday driving the I-5 highway. Almost 9 hours of highway driving resulted in 11.7 L per 100 km in a stock 2011 Ford 6.7. Pretty impressive fuel economy numbers for a 4 door 4 wheel drive 2011 F350 diesel. Truck and tuning are stock – the only mod is an S&B cold air intake. By the way, 11.7 L/100 = 20.1 mpg.