My 3.5 litre petrol M-B 350 CLK does approx 15 lph at 80 knts compared to my Auster which did approx 18 lph at the same speed. The Auster went in straight lines but the Merc is a lot more comfortable.
Wish my Auster would do 18 lph mines more like 30 for which she delivers 85 kts