I bought a one year old, 2009 ML320 CDI Bluetec about 18 months ago with just under 10,000 miles. I have 47,000 miles on it now. I average about 27.5 mpg and routinely get over 650 miles to a tank (~22 to 24 gallons at fill ups). It has been rock solid. My only issues have been with the refilling procedure for the AddBlue stuff. You have to fill the tank to rim to get the sensor to do its proper sensing function and turn the alarm off by itself. If you don't, it causes a malfunction that the dealer has to reset. And, in an ML when the "add" AddBlue light comes on, it takes about 5 gallons. The stuff is available at nearly every auto parts store now. So far, a great vehicle. OEM tires are horrid though (run flats on an SUV give the impression they are made from pine or oak).

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)