Urgh, mpg is only getting worse on c220, thoughts ?

[Den656]

Hi all ,I bought a 2006 w203 cdi c220 last month, when I bought it I suspected that the thermostat was duff, had this replaced and the car gets up to temp after approx 9 mins so pretty good I thought , after a steady cruising on the motorway at 60 the mpg would creep up to sometimes 41 mpg ,
However I bought some of the millers ecomax as it seemed to have favourable reviews but my mpg now only gets up to about 36 mpg, I have done about 150 miles since putting it in, should I be worried lol ? Tyre pressures etc all the same , any thoughts appreciated , cheers .

 

[V12]

1. Ignore the obc, do a tank to tank measure.
2. Ambient temps play a huge factor in mpg...along with traffic and other stuff..

 

[Frugal]

Agree with V12's comments above, also I notice a slight drop in mpg between summer and winter deisel which has been sold for over a month.

 

[A-AvantGarde]

Yes, as stated by V12, the ambient temperature play a huge factor in mpg, you don't state your location but I'd suggest that the reduced MPG is quite likely to be linked to the temperature drop.

 

[Den656]

Thanks for the replies chaps, I live in birmingham with regular commutes to Telford do do a 35 mile trip 3 to 4 times a week , when I start from cold the obc shows figures like 26 mpg but once warmed up they are better .
I usually use the display as a guide and it does seem to be pretty accurate , before the millers from a full tank I got about 450 miles , in your opinions is this good , average or bad lol ? Thanks again .

 

[m2287]

I get from 450-500 miles to a tank in my mrs c220 cdi... Mixed driving.

 

[dubsR33]

I'm pretty sure it must be weather related..

when i picked mine up from Manchester few weeks back the drive back it was in the fifties constantly and now its always around the mid forties..
hmm

 

[Den656]

Thanks for the replies chaps , will keep doing the millers and do a tank to tank , will come back whining if no improvement lol , thanks again .

 

[Barker44]

I usually get about 500to a tank out of mine but I have a heavy foot

 

[Billigmeister]

it doesn't sound too bad to be honest - like others say it will be down to the type of driving and overall average speed you do.

i find there is probably a good 2-3mpg drop off in the winter

 

[Rory]

it doesn't sound too bad to be honest - like others say it will be down to the type of driving and overall average speed you do.

i find there is probably a good 2-3mpg drop off in the winter

We get a lot of threads like this and I do feel there must be more to it than the usually obvious causes - I'd be be pretty devastated if, like the OP, I sat on the motorway at 60MPH and could only nudge the MPG to 41MPG!

Ruling out the things like tyre pressures and the brakes dragging etc, surely things like injector condition must make a difference? Can the injector timing go off a bit, or maybe the valve timing if the chain is worn?? Perhaps less than perfect compression ratios make a difference, or the MAF sensor not performing properly???

 

[Julesprivate]

Coincidently (apparently) I put a dose of millers in my c270CDI on Saturday. 92 miles later injector seal number 1 let go. Over that 92 miles the display showed 44MPG which is about right for the road/traffic at the time.

Personally, I think the Millers loosened off some carbon (which is in part what it's supposed to do) and that exposed a weakness in the injector seal.

I also found the car had turned into a Red Arrows display team member and smoked so much I felt like James Bond!

I've replaced the seal but haven't had a chance to drive it yet, I'm off to Germany and back this weekend so hopefully the rest of the seals won't go! (I didn't have time to do them all last night by torchlight).

Most people tell me it's a coincidence - personally I'm not so sure.

you don't have a smell of exhaust fumes in the car do you? how about excess smoke?

I know thousands of people have used that stuff with no negative issues, but to me it's a huge coincidence..

I average 48MPG but my commute is 55 miles each way, 46 of it motorway..

I did manage 61.1 last week, but that wasn't fun at all!

 

[Julesprivate]

re-reading yor post... And trying not to be a doomsayer but can i suggest you do a leakdown test?

The amount of compression you lose when an injector seal goes is quite impressive, mine started running like a 4 pot - which in effect it almost was at that stage..

 

[Rory]

I also found the car had turned into a Red Arrows display team member and smoked so much I felt like James Bond!

How much did you put in?

I used a few bottles of it but stopped as it didn't seem to make any difference to either MPG or how the car ran.

 

[Julesprivate]

How much did you put in?

I used a few bottles of it but stopped as it didn't seem to make any difference to either MPG or how the car ran.

Exactly as per the instructions, i used their special bottle to measure a dose for a 50 Litre tank, and then I immediately filled up to the max..

It may NOT be the Millers that did it... but I did 3000 miles in the car over the last 4 weeks since I bought it with no issues.

To be fair i did have it remapped 3 weeks ago but I've done ~2000 miles since then with no issues, and only 92 since the Millers went in.

Sorry OP - I didn't mean to steal your thread..

 

[renault12ts]

Why do we get threads like this...giving only half the story...450 miles per tank. Useless!! HOW BIG IS THE TANK???

 

[markjay]

Why do we get threads like this...giving only half the story...450 miles per tank. Useless!! HOW BIG IS THE TANK???

I believe he expected fellow 2006 C220cdi owners to offer their views on the range he achieved.

 

[Den656]

Thanks for more input chaps ,and renault12ts, as Markjay said. I am ideally asking views of other cars of the same marque as my own for comparisons , no point comparing fuel tank size as if I was comparing mine to that of a v8 petrol ,even if fuel tanks were equal size, there would be a vast difference in mpg.
Jules, thanks for the reply , I am not too happy with the mpg, hence me querying it as I did expect a fair bit better from the Merc, so a tad annoyed , wdm is a Merc Indy specialist so may give them a bell after Xmas to see about this leak down test, I did have them look it over when I bought the car,and it had no errors on star , and I know the top of the engine where the injectors live was all clean,so no apparent risk of the Black Death .
I know temprature plays a part in mpg , but I found the forum prior to buying the car ,and the mpg seemed pretty reasonable , but for some reason my car wants to pretend to be a petrol lol , and not give me decent mpg , last week I did a full tank ,and from red to red I got 450 , and that was with about 90% careful driving, no heavy acceleration or weight in it , so feeling a bit miffed to be honest! cheers all for taking the time to offer advice .

 

[m2287]

Thanks for more input chaps ,and renault12ts, as Markjay said. I am ideally asking views of other cars of the same marque as my own for comparisons , no point comparing fuel tank size as if I was comparing mine to that of a v8 petrol ,even if fuel tanks were equal size, there would be a vast difference in mpg.
Jules, thanks for the reply , I am not too happy with the mpg, hence me querying it as I did expect a fair bit better from the Merc, so a tad annoyed , wdm is a Merc Indy specialist so may give them a bell after Xmas to see about this leak down test, I did have them look it over when I bought the car,and it had no errors on star , and I know the top of the engine where the injectors live was all clean,so no apparent risk of the Black Death .
I know temprature plays a part in mpg , but I found the forum prior to buying the car ,and the mpg seemed pretty reasonable , but for some reason my car wants to pretend to be a petrol lol , and not give me decent mpg , last week I did a full tank ,and from red to red I got 450 , and that was with about 90% careful driving, no heavy acceleration or weight in it , so feeling a bit miffed to be honest! cheers all for taking the time to offer advice .

How far do you drive on a typical journey? My C220 seems to do 450-500miles to a tank, this involves a couple of 60 mile trips, but mainly a 22mile trip to work (4 miles of which are pretty much stop start) and then the same back again...

Im sure that if I used it to drive a long way, I would achieve a much higher range. I think its a 12 gallon tank and that would mean 500/12 = 41.6MPG, the stats say it should achieve 42.8 combined so im not far off and its done almost 170k.

 

[Den656]

Hello chap , I do a 15 mile journey to work which is mostly on the m6 with its 50 limit, then I also do 6 trips a week to Telford which are 35 miles each way , I don't do much stop start traffic bar my route to get onto the motorway which is approx 2 miles .