C220 CDI 2012 Executive Auto Poor MPG

[mercowner]

Hi All,

Hope someone can help me please. I purchased a C220 CDI Automatic mainly for motorway miles but I do some urban driving also and I am pretty disappointed with the MPG. I understand one can rarely achieve manufacturers claimed MPG but I am getting around 30MPG mainly driving around 30-40Mph with some stop start traffic. I have driven with stop/start on and also whilst switched off and I am not getting much better than 30.2 which to me seems poor as the stated MPG by Mercedes is around 47 so I was hoping at least close to 40.

This is my first German diesel...always owned manual petrols before. The car has 98k on the clock mostly Mercedes services history and drives pretty spot on. Its just the fuel economy seems pretty poor.

Is there something wrong with it? What can I check?

Thanks all for your help.

[Super Slo Mo]

Are you just getting your figures off the car’s computer? They are largely meaningless unless you have ‘calibrates’ it by doing some tank to tank fills and logging the mileage.

That said, it does sound a bit heavy for around town, but there are so many variables it’s difficult to be sure. Could be the way you are driving it.
Mine (E320 cdi) is dreadful around town, mid 20’s at best. Around 40-42 on the motorway at 70 ish. They are real figures too.
I would expect your car to be able to get comfortably into the 40’s on the motorway, although again it depends how you drive. Hard acceleration and high speed (80 plus) will have an effect.

[dave_s13]

Sounds thirsty,

My E350 S212 did better than that.

I would look at swapping out the thermostat as a 1st step. They often fail and don't allow the car to get up to optimal running temperature.

You can check the temps by buying a cheap bluetooth OBD reader and the torque app on your phone to get live coolant temp data. It should hover around the 90degree C mark.

[mercowner]

Thanks guys for the real quick replies.

I have filled the tank to full so I will see how much I get. But at the moment I am just going by the trip computer. I also see the consumption graph whilst driving which also shows distance left which is up and down like a yoyo. This obviously depends on traffic as I can see the figures just dropping if I am stuck in traffic for a few minutes but once driving it climbs back up.

Would the thermostat issue show up elsewhere like rear screen heater? It takes around 20 minutes before the temp moves upto 80-90c in the gauge so I assume this is normal for a diesel?

I have been driving it pretty gently, keeping the car going on momentum as much as possible and just touching the gas pedal to keep up with the speed limits.

[anonymous-user]

This wont be much help but I have a similar issue with my C250 (2014).

Urban (well country to be honest) 30-38MPG
Motorway: 40-50 MPG

Blahh

Edited by anonymous-user on Monday 19th November 13:26

[dave_s13]

Thermostat has nothing to do with the rear screen heater.

In my E350cdi, when I had it that is, it would take about 10mins for the needle to get to temp and then stay rock solid. I changed my thermostat for similar reasons to you; I also noticed the temp gauge was moving about a bit.

New stat, and a full service and the MPG improved a fair bit.

Best way to see what's going on is to plug in a code reader as I said. Btu changing the stat at nearly 100k miles could be considered nornal maintenance. It's really quite easy on these and they aren't mega expensive from mercedes.

[niva441]

The 2015 220 CDi coupe I had was generally between 45-50 mpg, but then I don't do much urban work, In urban conditions I would expect about 38 mpg. With the temperature dropping it did take some time to warm up, approx 10 miles, with 5 of those miles at 70 mph.

[eldar]

Pigdoguk said:

This wont be much help but I have a similar issue with my C250 (2014).

Urban (well country to be honest) 30-38MPG
Motorway: 40-50 MPG

Blahh

Edited by Pigdoguk on Monday 19th November 13:26

About the same as my 2012 C250. Perhaps 45 to 55 motorway. The on board computer was about 20% optimistic.

[Sheepshanks]

mercowner said:

This is my first German diesel...always owned manual petrols before.

I've got an older C270CDi. Ideally you've got to get these cars up to speed reasonably quickly and the just "waft" along, with your foot off the gas as much as possible. It works fine for me as I'm mostly in semi-rural flowing traffic, but it's tough in town/city driving.

The other thing is these cars take a lot of warming up if they're not under much load. Well into the teens of miles, or pretty well forever if you're in stop/start traffic. All diesels are like that - my wife's new Tiguan will show water temp at 90C in 4 miles but it's lying - it also shows the oil temp and it's 15 miles before that gets to 90C.

Which autobox mode are you using? Mins only has C & S, which is Comfort and Standard. In C it's lifeless and it feels a real struggle to get going as it starts in 2nd - I always use S, but that tends to hang on to gears a little longer before shifting up.

Does the car have a booster heater (set in cluster computer)? I leave mine on auto and it kicks in when the outside tmep is 8C but it puts a very hefty load on the alternator and impacts MPG. The upside is the heater is blowing warm air in 400 yds. Yours may have a different system.

[buggalugs]

I have a 2008 C220 CDI Auto, it’s a W204 same as yours but with the slightly older OM646 engine, yours will have the OM651 I think.

I get anywhere from 35-40 mpg in traffic around town, and at 70 on the motorway about 50-55.

It takes approx 10-15 minutes to get to 80C in the mornings

When I bought it it did have a faulty thermostat, it would rarely warm all the way up and would cool down again on the motorway.

All in all I get around 600 miles to a full tank, the low fuel warning comes on around 550 miles usually.

[Jasandjules]

My C300 is supposed to get about 65mpg. I get 47 average... ... I asked on the Merc boards and no-one really has an answer....