My '09 just rolled over 170,000 on the original equip except brakes and tires. How they're maintained has everything to do with the answer to your question. Granted, mine is an M-class vs your E-class finds, but the engine is the same. The 320 was a pretty solid powerplant in both gas and diesel versions. One question to determine is the AEM recall: is it a candidate and if so, has the work been done. My wife and I both drove '05 E-320s for several years. I don't think the 350 was an improvement; it had several issues unique to itself.