Recently acquired '89 300E with 105K in excellent well kept condition only averages 17.7 mpg cruising at 80 MPH on a daily 100 mile jog. Smooth running pleasure to drive. Does not get better at 65 to 70 MPH. Had recent coil replacement and regular dealer service. What are most likely items to check out to get normal economy? No oil consumption. Previously owned by 2 middleaged ladies and then a conservative banker. All maintained the car well.