270cdi or 320cdi - advice sought please

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New Member
Jan 31, 2017
W209 CLK270
Hello, I have started looking for a low mileage (sub 150k km) lhd car to replace my 2005 270cdi CLK that was written off in Spain last month. Although I would have been happy with an E Class or C Class with the same 270cdi engine when I bought this car, I ended up with the CLK because these cars frequently have lower mileages.

If anyone on the forum has personal experience of both the engines in the same car type i would be interested in your feedback on fuel consumption. I would expect the 320cdi to be worse, but given it has a 7 speed auto gearbox am wondering what real life penalty there actually is.

Also if someone has experience of working on both engines or can comment on the reliability of both I would be most interested.

Having read quite a lot on the internet I am inclined to stay with the 270cdi. In the 3&1/2 years and 60k km I had mine (written off at 153,000km) apart of all scheduled servicing and then some, I only had to replace a gearbox connector and an intercooler hose. Also apart from when towing it averaged about 6l/100km on the computer.

However if I open up my search to the 320cdi there are a lot more cars out there, and from everything I've read I will have a smoother, quieter and more powerful car for little difference in price.

The 320 L6 with 5 speed was the best engine. This v6 om642 isnt fuel efficient at all in comparison.
Yep om648 all day long
If I'm not mistaken that in-line 6 was installed in E Class and CLS but not CLK, is that correct?
If I'm not mistaken that in-line 6 was installed in E Class and CLS but not CLK, is that correct?


I never had those engines at same model, but like you see in my Car history, some experience about those engines :)

Overall I would say one mug more makes 0.5-1 L/100km more. And like above, OM642 feels bit more thirsty than OM648.

Full year average consumptions of my cars have been W210 7 L/100km, W211 7.5L/100km, W220 7.9L/100km, C219 8.5L/100km (after remapping perhaps 8.2L), W212 not anough data yet. Tyres make easily 1L/100km difference (bigger and wider are way more worse, noticed when winter/summer tyres are clearly different sizes in my C219)

Edit: I would say at factory settings 270CDI has perhaps best power feeling/consumption ratio, but remapped OM642 is... just great :)
Thanks for the replies. I will be sticking with the 270cdi, though I fear it may be a long search....

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