I have a 2017 E300 sedan. Before that, I had a 2013 E350 sedan and a 2015 E350 sedan. I have always been interested in the gas mileage as displayed on the instrument panel. But, I never checked it until recently. Now I have driven 2289 miles while using 81.52 gallons for an average of 28.1 mpg. But, the instrument panel reads 29.4 mpg over this distance. That's 1.3 mpg off. I would have that the instrument panel reading should be better than that.