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Old 10-31-2013, 08:07 PM
markg612 markg612 is offline
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Join Date: Dec 2005
Location: The Bay Area via Phoenix, Chicago and Minnesota.
Posts: 377
I have one of each, 642-86K and 648-96K. The OM648 in the W211 is torque beyond belief, I get 36MPG Highway. The 648 is a 3.2L the 642 is a 3.0L The OM642 has a tighter torque band and requires a bit more finesse to hit the pull point vs rpm. The 648 just goes, and then it goes some more. The 642, despite being .2L smaller is rated higher torque and HP, but you'd never know it. I honestly think the new 2.1L twin turbo in the 2014 E350 goes quicker than the 642!

DEF is a buzz kill for me in the 642 E class installs, the ML did NOT have DEF until 09 strangely enough.

Having worked on both of this engines extensively, the 642 really flat out just plan f-bombing sucks for access. It's like a ball of rubber binders wrapped all together and you dig and dig to get to any and everything. the 648 is 60x simple to get to everything. I'm also finding the 642 to be more costly to repair. I just put a MAF and EGR on the 642 to the tune of $800 just in parts, (the V engine has two of everything, two air cleaners, two MAFs two this two that etc., the inline six does not.) and I still need to DAS it at the stealership to clear the fault. The turbo likes to leak oil from the MAF Y-pipe if it's not installed perfectly to the point it runs down the back of the engine and looks like a main seal leak, as does the oil cooler nestled in the intake V, which also likes to leak.

The 648 has been rock solid, like inline motors tend to be.

Additional considerations you may want to check, I believe the 07-09 W211s had the 7 speed, the 05/06s have the 5 speed. My 07 shifts a lot to find the right pull point, the 05 just goes, fast.

Far as the Chick-little sky is falling blather about the brakes, roll the dice. Set up a poll in the forum and ask how many 05/06 guys have ACTUALLY had a brake problem on an established car? For what I've spent on the 642, I'd take a 648 and electric brakes every day of the week and twice on Sunday.

You're call, but I'd find the lowest mileage 06 and jump on it, but that's me.
2016 GLE300d 4-MATIC 38K BROWN!
2012 S350 Bluetec==94k WHITE

2007 ML320 CDI==166K WHITE (FOR SALE)

Under new management:
2005 E320 CDI--140K--WHITE
1995 E300-Diesel-133.5K--THE CAR IS BLUE
1986 300SL--97.5K (European) AND WHITE. Back in Europe!
1991 190E 2.3-73K California Perfect.--WHITE
1995 E320-Wagon-159K--WHITE (recently scrapped)
1987 300D Turbo-213K--WHITE
1987 190D 2.5 Turbo-288K--WHITE
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