I own both a 2001 E320 CDI estate and a 2003 E320 CDI estate. The engines are ostensibly the same, the earlier one generating 194 bhp and the later one, 204. Fundamentally the later car gives significantly worse consumption than the earlier model overall but the difference is particularly large cruising at around 80 mph. At this sort of speed the later model shows consumption just under 35 mpg and older just under 40. It might be worth relating that on one occasion while the weather was very warm this summer (c30C), I achieved a figure closer to 40 mpg in the later car at around 80 mph. I know the later car is heavier but equally the aerodynamics are surely better and the engine fuel system a little more developed? The car is regularly serviced and I have already had the Air Flow Meter replaced which improved the consumption by a small margin (say 2 mpg). The fuel consumption is not terrible but given my mileage of more than 20,000 per year, the difference is getting toward £500. Your advice or assistance would be greatly appreciated.