poor fuel economy on E320 CDI

[BTB 500]

PS from memory the official "extra-urban" mpg test averages just 39 mph. So not a good indicator of motorway consumption, particularly with "less sleek" vehicles.

 

[Rory]

Hmmm, OK, I'll try your suggestion Rory, I've done it before and got about 40MPG on a run up the M40. Trouble is I never seem to hit clear motorways very often and when I do...well let just say that the MPG on the 320CDI falls off rapidly the faster you go!
It just feels weird going so slow with the speedo needle barely half way round the dial

It does, but clear motorways are when you'll get caught.

Lots of cameras on bridges on M40 & M42.

I generally drive at 75 now (120KPH on the marvellous metric display) - the irritation of driving slowly is countered by lack of stress about losing my licence.

 

[Soltan]

It does, but clear motorways are when you'll get caught.

Lots of cameras on bridges on M40 & M42.

I generally drive at 75 now (120KPH on the marvellous metric display) - the irritation of driving slowly is countered by lack of stress about losing my licence.

Fair point, I've found myself doing that a couple of time, thought I was just getting old
I like your version better

 

[jadefox]

I find that Trip Computers are one of the worst things devised in the car.

First car that I've had it in and you end up trying to drive to the MPG . Have to stop myself having it on the display now, otherwise I end up driving everywhere 55mph

I find it funny to a point as well about the MPG, all these people buying cars with 3 litre plus engines worrying about their MPG (though I do it too ).

 

[ckember]

my mate at work has a 200bhp golf gti, 10 days old, gets 40mpg on the motorway doing 90mph. I am sure I should be close to that in a diesel?

Is there any way of getting an instantaneous reading of the fuel economy, instead of the after start or total average?

by the way is there a hidden menu on the w211 to show number of litres of oil, voltage etc? There was one on the w203

 

[jadefox]

Your mileage does definitely seem a little short and even though your car is probably 1/3 heavier the difference should not be that great with a Golf GTI. After all, the Golfs Extra Urban is 45.6..... Yours is slightly higher at 47.9.

That being said, he is doing VERY well if he gets greater than the combined rating (35.3) at a consistent 90mph - I'm sure even VW would be impressed.

 

[timskemp]

I have a 57 E280CDi (which is based on a similar engine) with 2500 miles on the clock and am getting similar mileage and am similarly disappointed.

Admittedly I do quite a lot of urban driving and on the open road I can push the speed a bit but even the "bosses" best is about 33-34 and that is at a pretty steady 60-70.

So far this is no improvement on my petrol V70 and I'm paying 10% extra for the fuel

My Petrol S60 (2.0T, chipped) never saw more the 24mpg, seeing 20-22 most of the time (gives you a clue as to my driving style) - the E270 is seeing 27-30 in town, 35-40 out of town, averaging 32-34 overall.

Winter diesel affects economy, as does auxilliary heater (or fast idle if not fitted), as does driving style (a lot). The E280 I had on loan struggled to reach 30mpg average with my right foot, 40mpg being the best I had (gentle run from Colchester to Nottingham). Any driving at >80mph will probably see you dropping below 40mpg, but the returns are better at higher speeds (30mpg at 115mph in the E270, the Volvo would have been down below 20 at that point.)

Bear in mind too that the E is bigger than the Volvo...

 

[ckember]

I have filled to the brim today and calculated that the average was 25.7mpg this was a mixture of town, country roads, some dual carriageway and some motorway. I recon this is about 5-10mpg lower than expected.

I also checked the oil today and found that I have a dip stick and not the electronic version I had in the c270. the manual refers to this being available on the E class _anyone know which engines have the manual dipstick and which have the eledtronic version. The dip stick is reading atleast 75% full 5 minutes after the engine was turned off.

the manual recons on 0.8l/1000miles ,or higher on an new engine, oil useage.

 

[sweeper]

i have to say i am not impressed with the fuel economy of the diesel engines these days, after all i can get26mpg on a run (with a full load) out of my Jag cruising between 75 and 90 +, the merc 230K can give 35mpg on a long steady run with a full load and a roof box and my diesel van seems to do30-35mpg regardless of how i thrash it (and i do) so what is going wrong with the mercs these days, i was considering one but i really need better gains to make it attractive.

 

[DieselE]

Hmmm, OK, I'll try your suggestion Rory, I've done it before and got about 40MPG on a run up the M40. Trouble is I never seem to hit clear motorways very often and when I do...well let just say that the MPG on the 320CDI falls off rapidly the faster you go!
It just feels weird going so slow with the speedo needle barely half way round the dial

The M40 is a fast motorway and there is a temptation to "press on a bit"

On my last trip from London back to the midlands on that route, the trip computer showed 41.5mpg. The journey was 120 miles. The first mile (office to A40) took 15 minutes and the next 119 took 105 minutes.

Mind you my car is a well run in (46k+) straight six E320CDI and they are 5-10% more fuel efficient than the V6 versions.

 

[ckember]

I noticed today that on a short run about 4miles I got 27.5mpg never went above 50mph. I also noticed that the mpg starts off at 40mpg when I first start the car in the morning, then quickly drops to about 30mpg. I thought it should read much higher than that?

 

[merc07]

Take a look at the DPT Tuning units...

http://www.dieselpowertuning.co.uk/

I was getting 34-38mpg from my 2007 220cdi. I'm now on my 3rd tankfull since fitting it. The last one worked out at 45.3mpg. On a steady motorway run including about 7 miles of B road it showed 52, real world is 49.5

I have it set for Economy - also gives a slight increase in power/torque in low revs.

Cheers
Adam

 

[DieselE]

I noticed today that on a short run about 4miles I got 27.5mpg never went above 50mph. I also noticed that the mpg starts off at 40mpg when I first start the car in the morning, then quickly drops to about 30mpg. I thought it should read much higher than that?

In a four mile journey from cold, a diesel will not even come close to being up to temperature. Also, to achieve maximum fuel economy you need to be on a road where you can get the speed up to a level where the car happily sits in top gear on a light throttle. That 27.5mpg is fairly normal for round town driving which is what your short journey effectively is.

 

[Rory]

In a four mile journey from cold, a diesel will not even come close to being up to temperature. Also, to achieve maximum fuel economy you need to be on a road where you can get the speed up to a level where the car happily sits in top gear on a light throttle. That 27.5mpg is fairly normal for round town driving which is what your short journey effectively is.

Agree with that - in cold weather the temp gauge would only just about be moving off its stop at 4miles. Also the car is probably using its auxiliary heater which isn't going to help.

We're lucky enough to have several little cars in the family and I generally use one those around town - I wouldn't take the Merc unless all the other cars were out.

 

[ckember]

if i had an aux heater shouldn't i be able to turn it off in the settings menu. Is the aux heater an option or standard on the E class. I know on my c270 I could turn it off


Just spoke to the local dealer, he said that apart from a fuel leak, which I cannot see at the moment, he cannot think of any reason apart from its too new and to let the engine loosen up more. They wpuld also need it for a day or more to check the mpg.

I guess a track day may help!!!

 

[Satch]

From a cold start find my E320Cdi needs at least 10 miles of A/B road driving to get up to temperature and the displayed fuel consumption figure will be around 30mpg

MPG does not start to look more respectable until 20 miles+. Have to face up to the fact that an E320Cdi is not the weapon of choice for short haul or stop start motoring

If by "Auxilliary Heater" you mean the one for the cabin that cuts in in cold weather, that is a electric ceramic heater (effectively a oversized hairdryer) and is disabled when the A/C is "off".

 

[Dryce]

From a cold start find my E320Cdi needs at least 10 miles of A/B road driving to get up to temperature and the displayed fuel consumption figure will be around 30mpg

ISTR a thread discussing merits of petrol and diesel and it was asserted that diesels start working more quickly than petrol engines (ie. diesels better on short runs).

It sounds as if at least some real world experience is different. I also wasn't aware of the fact that seasonal fuel consumption could vary so significantly.

 

[timskemp]

Satch - are you sure, I thought W211 cabin heaters were fuel driven not ceramic / electric.

 

[skemball]

Interesting about the pre-heater being disabled when the A/C is off.

Mine runs bang on spec' but on idle when trying to defrost the screen t takes forever for the heater to get even luke warm - I always have A/C off unless its needed.

Will give it a go tomorrow to see if it makes any difference.

 

[Chris_J]

Is that the Auxiliary heater or the Heater Booster? I've left mine on Automatic at the moment, but I'm sure there is an option to turn it Off and also Air-Con off. What does the last one mean? Does it mean Air-Con is disabled?