I've got a 98 e430 and took it for a road trip over the weekend. I averaged 27.4 MPG on the highway & got almost 540 miles from a tank of gas.... I was impressed, as this is better than my last car a 95 e320...... a V8 that get better gas mileage than a 6...... oh, the car has 56K on it, and I was thinking that around 60 K I would do the spark plugs and the O2 sensor... I'm thinking it may not be time yet.....