Poor fuel consumption on 203 C 220 CDi

[Baldrick123]

Your help please ladies and gentlemen.

My c220 CDi provides very poor fuel consumption. I also have a 203 c180 which returns 38mpg which I think is excellent, on the same journey the c220 cdi returns 39 mpg.

As mentioned in a previous post I took it to a main dealer who diagnosed the problem as four faulty injectors, which stupidly I asked them to replace at a cost of just over £1k. The fuel consumption remains the same.

The fuel readout reads an average of between 48- 50 mpg which is what I would expect. I just wondered if the fuel could be leaking from somewhere and I haven't noticed, the car does have a full undertray which might disguise a leak. I don't want to take it back to the main dealer as I have given them enough opportunities to solve the problem.

Any thoughts would be really helpful.

Regards

Andy

 

[rpe2]

Probably not a leak as it would be a swine to start.

39mpg is low-ish, but not terrible. Improvements may be gained from the MAF, and (strange as it may sound) a hard Italian tune up down the motorway.

Failing this, there are firms out there who will re-map your ecu to give better economy.

 

[Baldrick123]

Thanks for your help Richard. I have tried blasting it along a motorway, didn't seem to make any difference. Would a problem with the MAF be diagnosed via the star system?

Regards

Andy

 

[rpe2]

A maf can show as a fault, but not always. They can be cleaned using Isoprop' Alcohol. There is a method of testing, but I can't remember how (try a search on here).

Back to basics, is the air filter clean?

Also try working out an actual MPG, to see if it's the computer at fault.

Fill tank to brim, reset trip counter to zero, drive as normal for 400 ish miles, fill tank to brim, note mileage.

Actual consumption = x miles on trip counter/ gallons taken to fill tank at re-fill. [4.546 litres to a gallon]

 

[alindsay81]

My MPG reading is about 37, I need to fill up tonight so i will try this calculation then.

I feel that 37 is very low for a C220 CDI ?

 

[Baldrick123]

Thanks Richard the air filter is clean. I have worked out the actual mpg and for 400 miles I need to put in just over 10 gallons. It could be the read out is wrong. I just expected it to be far more efficent than my c180.

The handbook quotes mpg for the c220 cdi as:

Urban 32mpg
56mph 59 mpg
mixed 45mpg

My commute is very much 50 - 60 mph for 30 minutes along country roads with no traffic.

It is interesting that alindsey81 is getting similar figures, maybe the readout is wrong and the handbook is 30% optomistic.

Thanks for your help.

Andy

 

[jberks]

I also have a 203 c180 which returns 38mpg which I think is excellent, on the same journey the c220 cdi returns 39 mpg.

Computers tend to be a bit optomistic. You need real figures.I'd say 38mpg from a C180 is actually too good.
How hilly is your commute?
What tyres are you running on and what are the pressures like?
Whats the temperature like (a cdi will have a pre-heater that will murder fuel economy in the short term in cold weather).
How do you drive it? A 180 is quite underpowered so it could be that you sit back and cruise. The 220 is more gutsy, especially when the turbo is 'on' so you may use it more. I was discussing with the tyre fitter, why turbo diesel mercs eat rear tyres. Its not the car, its the driver enjoying the turbo kick that does it.
Lots of variables.

You have to remember that the fuel has to go somewhere. If it's unburned then it will show up on the CO2 or smoke MOT test. If it's leaking it will be obvious (or you'll slide off the road) and given the pressures you'd be seeing 10mpg not 40. So, it's most likely its being burned efficiently and you're simply using that energy to drive the car and overcome friction and inertia. I'd get 5mpg better if I swapped my 245 khumo tyres to 225 Michelin Energy tyres for example.

 

[Baldrick123]

Thanks J Berks

The 38 mpg for my c180 are real figures. I try to drive both cars the same, I live in essex so fairly flat, but I agree the cdi takes a long time to get warmed up and never goes above 60 degrees.

I try to keep the tyre pressures at 32, as I thought this was originally the problem. The tyres are goodrich's

It would be interesting to know what other people are getting with their 220 cdi's

Thanks for your comments.

Andy

 

[jibcl500]

a new air flow meter is roughly £60 from Mercedes easy to fit, diags may not show a fault with it but the are classed as a service item!!!

Also when was the last service done? might be worth checking the brakes as a binding brake will increase fuel usage.

jib

 

[Alex M Grieve]

It would be interesting to know what other people are getting with their 220 cdi's Andy

Hi Andy. What mileage has your car done?

We have a 220CDI which has just hit 10,000. Until now it has been reluctant to do better than 38 mpg, and it has not had a hard life. As it eases over 10,000, we are now seeing journey averages in the 40s and I had a run of about 240 miles where it showed 48.

Cold weather and cold starts don't help. Tyre pressures you have covered. The other great trick is to aim to drive it at optimum torque - just on 2,000 rpm, which should suit your commute perfectly.

It will be interesting to hear how you get on.

 

[rf065]

the cdi takes a long time to get warmed up and never goes above 60 degrees.

That does not sound right?
Mine always sits around 80 to 90 degrees.

Russ

 

[Nuclear Bob]

My C220 CDI coupe (manual) always achieves 50 to 55 mpg (measured - the indicator is 58 to 63 mpg). Slightly more economy in winter - 1 or 2 mpg - since I changed the thermostat - mine too was getting no higher than 60 deg -now around 85. I don't drive slowly but I do have an eye on economy as I do over 30000 miles a year.

 

[alindsay81]

That does not sound right?
Mine always sits around 80 to 90 degrees.

Russ

Mine has 34k miles. its a 2005.

Temperature sits at 90. My VW Golf GTITDI 150 also sits at 90.

I have the heater option set to automatic, so i guess this use's fuel in the mornings ???

 

[alindsay81]

Calculation performed this morning,

Trip Miles 411.6
Litre To Fill 52.2
Gallons To Fill 11.48
MPG 35.8

Computer said i got 36.0 MPG so i guess its fairly accurate in this case.

It seems there are improvements to be made!

 

[Blakey]

If it never warms up then it sounds like a new thermostat is needed, unless you are only doing short journeys.

Chris.

 

[Baldrick123]

Nuclear Bob's point is interesting, I wonder if the car isn't warming up to the correc temp. Mind alindsey is only getting 35mpg at 90 degrees.

Alex my c220 had done 80k.

Thanks all.

Andy

 

[w mckeown]

good fuel economey

I have the same car c220 2003 model had it chipped and went to scotland and back over weekend 1050 miles and i was doing normal 80 mph on motorway average over whole weekend was 55 mpg. i do a daily commute of 40 miles and normally get 45 - 48 mpg. could be because of the chip i get better mpg

 

[wireman]

the cdi takes a long time to get warmed up and never goes above 60 degrees

Time for a new thermostat.

Regardless of it making any fuel consumption improvements, engine part consumption will increase at low running temperatures.
Given a few thousand miles of running cold the oil consumption will rise indicating that the engine is wearing out...

 

[Baldrick123]

Thanks for your help Wireman

I will investigate reneiwng the thermostat. Will use and indie rather than a MB dealer!


Andy

 

[survey]

My auto C220cdi W204 2008 model year has only covered 6500 miles. This has averaged 41mpg (actual) and the computer reads 44mpg overall. At each fill-up the tank mpg is slowly improving. The car certainly prefers to be driven at 60-70mph. Cold starts and short runs drops the running mpg to 38ish but this is quickly recovered to the mid 40's when on a run.

I have driven diesels for years and reckon that they do improve consumption as the miles go on.