I hate to say this but...after almost 40 years of driving primarily Fords & Volvos (and a Chevy once but I rarely admit to that), I can honestly say the only vehicle that has EVER stranded me on the side of the road, dead in the water, is a Mercedes.

I have a '99 E320 and what happened was the drive belt tensioner pulley failed and threw the belt. Dash warnings told me the of the belt problem and I made it to an area with NAPA, Advance Auto & O'Reilly parts stores.
No problem getting the belt, they all had one in stock, so with my toolbox in the trunk, I felt on top of things but... when I opened the hood and saw the belt was still intact, just off the pulleys, I looked harder and lo, the tensioner pulley bearing was no more.

No one had one, not only that, they didn't even have it at a local distributor, it had to be ordered direct from the supplier, not to arrive until sometime the following week (this was a Saturday, natch). Can't just get a pulley either, have to get the whole tensioner assy. the closest MB dealer was on the other side of Atlanta so no hope there. I had to flatbed it home. Disgusting turn of events for someone who prides himself on being prepared for such events as this.

Anyone else have tensioner pulley problems? What is the expected life of these? They are good for 100k on Volvos, this one had less than 50k. There was no warning, no whine, rumble nor clanking. It gave up the ghost while I was idling at a stop light after a 45 minute, 45 mph run in Drive.

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1999 E320 (gave to daughter) 250K
1994 F150 (may be the end of its road) 240K
1989 560 SL (Reassembly after paint job) 160K
1986 560 SL (deceased., gave it's life protecting my wife)
1988 300 TE (departed)
1994 945T (still running strong with an upgraded cam) 349K
1986 242Ti (deceased)
1968 GT500KR (under restoration)