I used to be a Paramedic and we had the OM642 in the sprinters and those engines were hammered. They would go from cold to very high revs all their working life. Many ambulances went to auction with 550.000 miles on the clock and had issues what so ever. I think Mercedes is still a high quality brand but they need to be respected and properly serviced. My W211 is nearly 160 k and nothing really has gone wrong in the last 10 years. The only problem is they are quite complex electrically, and also the SBC pump. Mine is still going strong at 18 years and I don't see her going anywhere yet. We used to have Peugeot, Renault ambulances also and they were always going wrong. They cant hold a candle up to a Mercedes. Many ambulance services have gone over to Peugeot because the sprinters are too expensive, the only trust that still buys new sprinters is London Ambulance