KEN - I stand corrected on the thermostat issue. I barely see 80 degrees even after climbing (pretty steep - 1 mile? long) hill going home. Even on the freeway - the temp is UNDER 80, CLEARLY. Will this affect MPG that much? What about EGR? (If it's stuck open? I have to check to see if it is - I have capped vac line to EGR.) Do you know if fuel injection pump could be wasting fuel somehow? - I'm still trying to understand the bad MPG. Without compression test (yet), don't know if that would be the culprit. Again, and maybe this is of NO consequence, but the car does do highway speeds nicely, but again my other car is a Volvo, and this is my first MB. Thanks again!