54-c220 cdi 15k poor fuel economy ~30 mpg

[stompa]

Hi,
i bought a 54 plate c220 auto in April (~5k miles) and its allways had poor fuel economy. I was getting ~35 mpg when it went in for its first service (18 month max service interval paid for by merc) & i querried it with the garage i bought it from, the garrage it was serviced at & merc customer service who all said the car was still running in and was nothing to worry about. i've since done ~10k miles including 1k mile trips to scotland and wales but the mpg is going down i'm now getting 29 or 31 mpg if i'm really careful. i know i should be getting 50+mpg on long runs but i'd expect 40+ on short runs too.
anyone else had any similar issues? any suggestions to improve economy?
i use either shell or bp ultimate diesel.

Chris
c220 54 auto

 

[Dieselman]

For a start have the MAF, EGR valve and intake flaps checked.
As you have said this is poor economy.

Does the gearbox always change up the gears quickly if at all. A collegue had an E220 that would hold third gear for no reason resulting in poor economy, 35 average.
The dealer and MB tech were unable to resolve his issue so he sold the car.

One bit of advise would be to give the car a really hard thrashing up some steep hills. You might be treating the engine too gently so are clogging the cat and causing bore glazing.
If you don't feel like thrashing your car mecilessly then lend it to me for a week.

 

[Parrot of Doom]

If you don't feel like thrashing your car mecilessly then lend it to me for a week.

lol.

 

[RichardM]

Hi,
i know i should be getting 50+mpg on long runs but i'd expect 40+ on short runs too.

I'd have thought you'd get 40+ on a long run and only low 30's on short runs.

 

[Wully]

I've a 2002 C220 CDi and out a full talk i average around 35mpg according to the trip computer. This normally consists of around town driving and short 19 mile trips on the motorway.

On a brighter note i did take it for a 600 mile round trip and when staying at an average of around 65mph i got high 40's.

I've always thought i should get more but just put it down to the town driving causing the problem.

 

[mark.t]

For a start have the MAF, EGR valve and intake flaps checked.
As you have said this is poor economy.

Does the gearbox always change up the gears quickly if at all. A collegue had an E220 that would hold third gear for no reason resulting in poor economy, 35 average.
The dealer and MB tech were unable to resolve his issue so he sold the car.

One bit of advise would be to give the car a really hard thrashing up some steep hills. You might be treating the engine too gently so are clogging the cat and causing bore glazing.
If you don't feel like thrashing your car mecilessly then lend it to me for a week.

or me

 

[compress ignite]

fuel consumption

Hello,

Please try measuring your mpg/lpk as a function of actual fuel used ,when
filling tank against the actual milage/kilometer figure shown.
The "E"lectronic milage/kilometer guages are a fantasy reference point.

 

[Wully]

Hello,

Please try measuring your mpg/lpk as a function of actual fuel used ,when
filling tank against the actual milage/kilometer figure shown.
The "E"lectronic milage/kilometer guages are a fantasy reference point.

That's exactly what i'm in the process of doing, so far saved every receipt for full since i purchased the car and recorded mileage etc.

Just need to get wrong to working it out!

 

[Harley Man]

I've a 2002 C220 CDi and out a full talk i average around 35mpg according to the trip computer. This normally consists of around town driving and short 19 mile trips on the motorway.

Looks like C220CDi's vary dramatically, my one (2001 auto) averaged 42mpg over 112K miles, and on a decent run (100 miles plus on the motorway) crusing at 80 it would do 50 - 52mpg, I checked the onboard computer many times and found it to be pretty accurate.compareing the speedo against a GPS showed that to be very accurate too.

sounds to me that you may need a new MAF sensor?

Dave - Harley Man

 

[fredfloggle]

Mine is averaging 42.5mpg - will go as high as 47 ish on a long run without too much caning (average speed 76mph) - but don't hope to get that on short local runs , especially if the booster heater is on - around 35mpg in those circumstances .

They do differ , my last one seemed a bit more economic than this . It also depends on the amount of rust that has already dropped off .

 

[stompa]

many thanks for all your reply's.
i've read all 17 pages on the merc owners forum here & this is what i've gleaned:

• merc added a particle filter in 2004 to meet EU4 regs in the 200/220 engine, which reduced fuel economy.
• EU4 engines use different oil from EU3 engines
• some early EU4 220's where 143ps the rest are 150ps
• the particle filter gets coated in soot and the car needs a good thrashing to remove the soot. is it best to do this with a cold or hot engine? should i leave the car in neutral and rev it or whilst driving, get the auto box to go to the lowest gear and floor it?
• in top gear, 2000 revs is about 60mph whilst cruising and about 2200 when accelerating.

my car appears to not go into overdrive or even the highest gear especially when travelling at 30 mph and never with cruise or speed limiter on. i've noticed that whilst driving in d if i knock the lever to the right the car will go into the next gear sooner so i can take more advantage of the in gear torque available (i would expect the auto box to move to the most economical gear available asap)

i reset the last reset trip when i last filled up & will check milage/litres used when i fill up tomorrow.
i drove to bexhill on boxing day ~110 miles mainly duel cariagway and motorway at ~80mph and averaged 34 mpg. on the way back yesterday i averaged 38mpg at ~80mph pulling the gear lever to the right when i wanted a higher gear and flooring it every so often to try and clear the filter.

the car goes in for service in 2 weeks & had my comments added to the work sheet for the mechanics to investigate.
I'm considering writing to Merc to see if there's anything they can do as 34-38mpg on long motorway journeys isn't very good especially in a diesel. i got 44mpg out of my golf gti 1.8t in the scottish highlands (i was being especially good though)

 

[tikw2124]

My 270 CDi used to get 50+ on my comuting run of only 40 miles 50/50 A/dual carriageways. After changing a faulty MAF sensor, MPG now only 45 on same runs. Car has done 130k, uses Sainsbury diesel and is driven!

However, on reading this thread, i will try BP diesel.

Rgds

Keith

 

[Glenn Smith]

many thanks for all your reply's.
i've read all 17 pages on the merc owners forum here & this is what i've gleaned:

• merc added a particle filter in 2004 to meet EU4 regs in the 200/220 engine, which reduced fuel economy.
• EU4 engines use different oil from EU3 engines
• some early EU4 220's where 143ps the rest are 150ps
• the particle filter gets coated in soot and the car needs a good thrashing to remove the soot. is it best to do this with a cold or hot engine? should i leave the car in neutral and rev it or whilst driving, get the auto box to go to the lowest gear and floor it?
• in top gear, 2000 revs is about 60mph whilst cruising and about 2200 when accelerating.

my car appears to not go into overdrive or even the highest gear especially when travelling at 30 mph and never with cruise or speed limiter on. i've noticed that whilst driving in d if i knock the lever to the right the car will go into the next gear sooner so i can take more advantage of the in gear torque available (i would expect the auto box to move to the most economical gear available asap)

i reset the last reset trip when i last filled up & will check milage/litres used when i fill up tomorrow.
i drove to bexhill on boxing day ~110 miles mainly duel cariagway and motorway at ~80mph and averaged 34 mpg. on the way back yesterday i averaged 38mpg at ~80mph pulling the gear lever to the right when i wanted a higher gear and flooring it every so often to try and clear the filter.

the car goes in for service in 2 weeks & had my comments added to the work sheet for the mechanics to investigate.
I'm considering writing to Merc to see if there's anything they can do as 34-38mpg on long motorway journeys isn't very good especially in a diesel. i got 44mpg out of my golf gti 1.8t in the scottish highlands (i was being especially good though)

What do you call overdrive? i'm assuming you have a 5spd auto, when you put it in D are you inadvertently pushing it to the left and losing top gear? The display should show which is the highest gear that is available ie 1 2 3 4 or D sounds like you may have a gearbox fault although i would't expect it to change into top at 30mph, a ork colleauge has an estate version on an 05 plate he averages 40mpg and he drives it! Rev counter always around 4000 during accellerating. Just as a comparison i get 30mpg out of the c230k and have managed this fully loaded with a loaded roof box at autobahn speeds.

 

[Rory]

[*]merc added a particle filter in 2004 to meet EU4 regs in the 200/220 engine, which reduced fuel economy.

that definitely has a slightly detrimental effect on economy

[*]the particle filter gets coated in soot and the car needs a good thrashing to remove the soot. is it best to do this with a cold or hot engine? should i leave the car in neutral and rev it or whilst driving, get the auto box to go to the lowest gear and floor it?

When it's hot - preferably by putting the engine under load, ie up a long steepish hill.

my car appears to not go into overdrive or even the highest gear especially when travelling at 30 mph and never with cruise or speed limiter on. i've noticed that whilst driving in d if i knock the lever to the right the car will go into the next gear sooner so i can take more advantage of the in gear torque available (i would expect the auto box to move to the most economical gear available asap)

I don't understand what you're saying there either. At 30, it's probably in 3rd gear. Mine doesn't drop into 5th until it's approaching 50MPH. It will change up at slightly lower speeds (and will generally be slightly more economical) if you drive with the auto box in Comfort mode. The downside of C is that you may find take-off from junctions etc altogether too leisurely.

i drove to bexhill on boxing day ~110 miles mainly duel cariagway and motorway at ~80mph and averaged 34 mpg. on the way back yesterday i averaged 38mpg at ~80mph pulling the gear lever to the right when i wanted a higher gear and flooring it every so often to try and clear the filter.

*Very* steady driving is the key too good economy in any auto. Ease the car up hills - let it build up speed down hills etc. Again, I don't get the pulling to the right for a higher gear thing.

i got 44mpg out of my golf gti 1.8t in the scottish highlands (i was being especially good though)

...and I bet it wasn't an auto.

 

[stompa]

Hello,
just to explain the nudging the gear lever to the right thing. if your driving in 'D' @ 30mph at 1500+ rpm, if you nudge the gear lever to the right the car will go to the next highest gear i.e 2nd to 3rd and drop the rev's to ~1100 rpm. if i do this procedure when the car is in cruise its quite happy in the higher gear and lower rev's until i need to change speed. try it on a stretch of road that your familier with.
i've had the car serviced and they replaced the MAF. It's made a slight improvement, but i've since done an ECU reset and have noticed another slight improvement since doing that too.
To be fair, the online manual is almost inline with the fuel economy i'm getting, which what the retailer said to me when i collected the car after the service.