C350 CDI om642 correct engine temperature?

[DSM10000]

The current cold weather will have an effect and with more load from lights, screen heater, heated seats etc
My W211 with an earlier version of the engine in your car averaged around 34mpg on mixed use. I did see 43mpg brim to brim on a 200 mile journey a few times.

 

[philnewmerc]

Good point. Temperature has plummeted since the thermostat replacement...

 

[DSM10000]

Good point. Temperature has plummeted since the thermostat replacement...

Plus you may have winter diesel in the tank which has a lower energy value due to the anti waxing additives

 

[E55BOF]

Three things to bear in mind: nobody ever attains the official test figures driving normally; Mercedes will have done everything they could get away with (make up your own mind whether 'Dieselgate' was actually out-and-out cheating, or just very sharp practice...) to minimize the fuel consumption on test; fuel consumption increases in winter.

I don't think you have a problem, and on a long motorway run you might well see 40 mpg at 70-75 mph. I would have in my remapped OM642 CLS 350 if I'd ever cruised at that speed...

 

[OneForTheRoad]

Not sure if you saw my mpg photo. Glc 350 4*4 . Over 281 miles sat at 65/75 mph I averaged 40.3 at best . Sometimes on cruise control.

 

[sautah]

I don't think you are driving far enough to get a decent MPG figure reading there. My 250 CDi can take an hour or more before it starts to read over 50 MPG especially after I have used it for some short runs or it's sat unused like over Christmas when I was away for 2 weeks holiday. In these instances it hovers around 38 ish.

As far as being 6 cylinder etc I also have a BMW 6 series diesel and that gets over 50 too on a decent run. Same issue though, You have to be on a proper run before it hits the 50+ mpg Driving it for 30 minutes or so just doesn't give it a chance.

 

[Isdyl]

Hi - I've just read this very interesting thread as I'll having a similar issue with my CLS 2013 350 cdi. The temperature always sits around 70 or 75 and I've ordered a new thermostat. However, I know from previous research that the 'Diesel Emissions Software Update' which I had done a few years ago makes the engine run cooler in order to produce less NOx. I just wonder if this could be anything to do with it? Why would a thermostat have a heater element in it? Could MB have programmed the heating element to make the Stat open earlier?

 

[OneForTheRoad]

Hi - I've just read this very interesting thread as I'll having a similar issue with my CLS 2013 350 cdi. The temperature always sits around 70 or 75 and I've ordered a new thermostat. However, I know from previous research that the 'Diesel Emissions Software Update' which I had done a few years ago makes the engine run cooler in order to produce less NOx. I just wonder if this could be anything to do with it? Why would a thermostat have a heater element in it? Could MB have programmed the heating element to make the Stat open earlier?

Afaik the temperature sensor talks to the maf and glow plugs to control emissions , not the opening , that's bi metallic and a spring affair.

 

[Isdyl]

Afaik the temperature sensor talks to the maf and glow plugs to control emissions , not the opening , that's bi metallic and a spring affair.

Hi - but there is also a small heating element like a mini emersion heater within the thermostat housing. What could that possibly be for?

 

[OneForTheRoad]

Hi - but there is also a small heating element like a mini emersion heater within the thermostat housing. What could that possibly be for?

It melts a wax block I believe . Could be ECU controlled opening for winter / summer.

Every Merc diesel I've owned has ran at 90 . New and old.

 

[E55BOF]

The mini immersion heater (which is to help with emissions while the engine is warming up, I believe, though damned if I can remember how...) is often the cause of the thermostat sticking open; small amounts of crystallized antifreeze can accumulate over time in the very narrow clearance between it and it's bore in the hollow central pillar it runs through, eventually causing it to fail to open fully.

I've had many Mercedes over the past decade, diesel and petrol, and they all without exception ran at 90 degrees once the engine had warmed up.

 

[Isdyl]

I got a thermostat (pattern part from local motor factors) for £64, and paid a mobile mechanic £60 to fit it. All good now & steady at 90 degrees.

 

[ALFAitalia]

I've had many Mercedes over the past decade, diesel and petrol, and they all without exception ran at 90 degrees once the engine had warmed up

This one does too now (wifes A Class)...been getting no higher than about 60 for last few months. Not that she said until I noticed it!