C350 cdi 2010

[Billy1980]

Hi all.

Just joined yesterday. I have recently purchased a mercedes c350 cdi. 74k on the clock, fmbh. I can’t seem to get more than 25 mpg and driving like miss daisy. Surely that’s a bit to low, anything worth changing to improve that?

I look forward to hearing from you all

 

[whitenemesis]

Welcome aboard!
What sort of trips are you doing? Does the engine get up to temperature (~90c)?

 

[Billy1980]

Thanks and nice to meet you
ATM the trips are local and no temp is not getting anywhere near that. Takes about half hour for it to get 90c.

I have had it serviced, so hoping that will make a difference. One thing I noticed, the air filter had not been changed since 2018. Mechanic showed me it was all black and definitely needed changing.

Not sure if mass air flow sensor needs changing.

 

[whitenemesis]

Diesels and short trips will never give great mpg. My C class wouldn't ever get warm around town and the mpg dropped like a rock! On long runs it was fine. It's just around town it's hard to work the engine enough to get it warm. A diesel won't warm up when idling..
Might be worth checking the thermostat is operating correctly, if stuck open the coolant will take an age to warm up.

 

[nickgar]

That's a typical mpg while the V6 engine is cold, especially in the colder months. Big capacity diesels are not very economical when cold. Once it gets up to working temperature that mpg figure will nearly double, especially at a steady speed.

 

[Billy1980]

Yeh I understand for local trips it’s not going to be great. But I was expecting it to be better than my 2002 bmw 530d msport!

 

[Billy1980]

That's a typical mpg while the V6 engine is cold, especially in the colder months. Big capacity diesels are not very economical when cold. Once it gets up to working temperature that mpg figure will nearly double, especially at a steady speed.

Thanks nick, will monitor it. Like I said a service was done this week, so hoping to see a slight improvement

 

[MrGreedy]

Half an hour to warm up seems an incredible amount of time, and I would be looking at the thermostat as a possible culprit.

I did a code scan on an SL a week or 2 ago and that flagged an error that the thermostat was taking too long to get to temperature. Stat was changed and warm up and mpg immediately improved (M272 V6, not OM642, but still).

Air filters on these cars are 48k miles or 4 years, whichever is first, but I personally would change at 12-24k or condition based on annual inspection.

 

[Billy1980]

Half an hour to warm up seems an incredible amount of time, and I would be looking at the thermostat as a possible culprit.

I did a code scan on an SL a week or 2 ago and that flagged an error that the thermostat was taking too long to get to temperature. Stat was changed and warm up and mpg immediately improved (M272 V6, not OM642, but still).

Air filters on these cars are 48k miles or 4 years, whichever is first, but I personally would change at 12-24k or condition based on annual inspection.

Thanks for that. Their is no lights on the dash, sorry a bit clueless about these things. Just worth plugging into see if anything comes up ?

 

[mersum1es]

As above, Air filter of these are collecting everything smaller than squirrel, I personally change them once per year.

I car has previously done very shorts trip only, there also could be frequent DPF regen going on, which rise MPG. That point of view scanning could be giving some info, how long time ago succesfull regen was done. Note that most universal readers won't do, SDS recommended.

 

[W1ghty]

Thanks for that. Their is no lights on the dash, sorry a bit clueless about these things. Just worth plugging into see if anything comes up ?

It’s not worth plugging in , it is worth getting on the motorway ,seeing )as everyone has said ) that the thermostat gets to 90 in a decent time and stays there .
Reset the mpg trip on the motorway when the car is up to temp and see what the car returns at a decent speed for half hour . If it’s late 40’s? mpg then there is nothing else wrong , it’s the journeys you are doing and you are then back to the thermostat question

 

[W1ghty]

Where in Surrey are you buddy ?

 

[Billy1980]

Where in Surrey are you buddy ?

Woking

 

[Billy1980]

It’s not worth plugging in , it is worth getting on the motorway ,seeing )as everyone has said ) that the thermostat gets to 90 in a decent time and stays there .
Reset the mpg trip on the motorway when the car is up to temp and see what the car returns at a decent speed for half hour . If it’s late 40’s? mpg then there is nothing else wrong , it’s the journeys you are doing and you are then back to the thermostat question

Ok will do. Thank you all, appreciate your advise. Otherwise I’m gona flog it and get facelift model. Which is what I was after but c350’s are rear.

 

[MrGreedy]

If your not doing regular 20+ mile trips, I would consider getting the V6 petrol. It will be less headache than short slow trips in a diesel with DPF.

I'm very fortunate that in our household, we have a 1.6 petrol Golf and E350CDI. Golf short trips and round town. Merc for mile munching.

 

[SpikyMikey]

If your not doing regular 20+ mile trips, I would consider getting the V6 petrol. It will be less headache than short slow trips in a diesel with DPF.

I'm very fortunate that in our household, we have a 1.6 petrol Golf and E350CDI. Golf short trips and round town. Merc for mile munching.

Petrols warm up a lot quicker too: on my S204 the temperature gauge is climbing towards 90 degrees within a mile of setting off ( although I suspect the oil temp takes a lot longer).

 

[W1ghty]

Woking

You have Ian @ Star Services, Caversham near Reading if you need an MB specialist recommendation. I think there are another couple near/in Reading as well

 

[Billy1980]

If your not doing regular 20+ mile trips, I would consider getting the V6 petrol. It will be less headache than short slow trips in a diesel with DPF.

I'm very fortunate that in our household, we have a 1.6 petrol Golf and E350CDI. Golf short trips and round town. Merc for mile munching.

That’s what I’m thinking, thinking of getting 120d for locals and leave the met for longer drives.

By the way just come back from a 11 mile local stop start journey. Temperature reached about 80 when I got home. I drove most of the time in manual. Got 30.5 mpg.

 

[fabes]

I just about get that in my V6 petrol MB
Not the best engine for you unless you are doing some decent runs.

The 4 pot alternative should add 20 to 30% to that if you do want to stay diesel.

Check that thermostat (or just change it for good measure) though, as our last diesel warmed up much quicker than you're quoting

 

[W1ghty]

That’s what I’m thinking, thinking of getting 120d for locals and leave the met for longer drives.

By the way just come back from a 11 mile local stop start journey. Temperature reached about 80 when I got home. I drove most of the time in manual. Got 30.5 mpg.

Your thermostat is goosed buddy