You can't forget that despite the higher fuel cost, diesels are way less needy. The M103 needs way more attention than the 617....as I've recently learned.
I don't like engines that need several sensors and computers to keep them running properly (or at all!)....it just leaves that "hmm...if a computer or sensor dies I'd be sitting at the side of the road" feeling in your mind.....not so in a diesel.
IMHO the 617 is way stronger off the line than a M103....The M103 is weak until it gets over 2000 rpm....then it pulls quite hard. (awesome!) The off the line torque just isn't there. I've mashed the pedal in 1st in our 300E and its pretty leisurely on taking off....no tire squeal thats for sure.....but the shift from 1-2 will break the tires loose/make the car squirm on dry road....when you're going at full tilt. There's something the 617 won't do.
If going for a gasser W126 I'd be open to any of them....probably the first I found for the best price in the best condition. M103 leaves tons of room to work on it....but the 420 has more power.
It'd be a hard decision...
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-diesel is not just a fuel, its a way of life-
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'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
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