While I had my 2005 MZ3 Sport in for the 80k service, the technician recommended a tune up and fuel service - said it would be good for my car and improve my gas mileage. Neither are true. Over 1500 km my mileage has been 12.9 litres per 100km; 12l/100;11.3l/100; and 11.6l/100. The gas flow to the engine seems to be constricted causing a quick deceleration and jerking in 1st, 2nd and 3rd. It doesn't happen all the time, but several times a day. When I shift down approaching a stop light, the compression does slow the car down to a point, but it would keep moving without a foot on the gas. When I brake to a stop, the engine revs up to 2000 before dropping back to normal.
Before I took the car in, it ran well. On a road trip from Winnipeg to Utah and Colorado in February, I averaged 10 liters per 100km over a total of 5000 km, at Interstate speeds, and carrying seven pairs of skis in a roof box .