C350 ~33mpg :(

[crockers]

Do DPF ruin the economy? If so can they be removed and the ECU reprogrammed?

 

[RichardM]

Do DPF ruin the economy? If so can they be removed and the ECU reprogrammed?

I thought it was only when they go through the regeneration process that they use extra fuel.

 

[@MARK]

Do DPF ruin the economy? If so can they be removed and the ECU reprogrammed?

Well I have been told by those who have removed them that they see an increase in performance so one would assume that if they are sapping performance then they are forcing the engine to work harder which must mean lower MPG

Of course the greenies are not bothered about running costs or MPG. They are bothered about emissions and that's what the DPF does.

My concern about taking the DPF off though would be at MOT time.

I thought it was only when they go through the regeneration process that they use extra fuel.

Again I believe this is making the engine work harder so a double hit when this happens.

 

[Dieselman]

DPF were introduced because of public perception of diesels being dirty due to particulates. This stemmed from inaccurate press, but the public lapped it up....they only have themselves to blame.

Of course removal of an exhaust restriction will assist performance and economy and removal of the super dose of fuel required for regeneration will help as well.

 

[crockers]

As for the MOT, surely if the ECU is coded for DPF removal emissions may be ok??

 

[st4]

I don't go with diesels needing a long time to give best MPG, or them using significantly more fuel in cooler weather.

It takes a least 30k miles to bed one in, and more. The difference between the 1st Mercedes I got when I first had it, then before I canned it for "the shed" it was noticably better once over 40k. Numbers wise at least 5% improvement.

I drive the same route to work everyday, I drive it as efficiently as possible to save money and in the cooler days struggle to exceed 38mpg. On a warm day this is in excess of 42mpg.

There is a bend in which I set a target. On a warm day above 15c you will have the OBC reading 37mpg by that bend. On a cool day (below 10c) the OBC struggles for 34mpg. As I do this journey at the same time, and drive in the same manner 200x + year I can tell you just from my wallet, fuel gauge and OBC there is a significant different in consumption.

I don't believe manufacturers quoted MPGs are terribly hard to achieve. I average 39mpg in "the shed" and that includes some very manic fast backroad driving and the occasional blast at speeds I dare not mention as well as miss daisy driving. Drive it normally at speed limits on a mix of roads, it will achieve 37mpg without any bother. I've even beaten the extra urban on my car multiple times although that was agonizingly tedious.

The latest Cdi give shockingly poor mpg figures.

Looking at some of the posts here, and other posters they are not terribly great, however they give a performance in terms of acceleration and top speed that a diesel engine designed 15 years ago simply couldn't achieve. Whether or not thats a) necessary or even desirable b) that they will last as well and be as reliable only time will tell.

However, in my view the performance is desirable (the acceleration is brilliant) but maybe not neccessary for a family motor and I don't think the engines will last without going through injectors and turbos every 100k-200k.

I also believe that now, more than ever, the engine is designed specifically with that test in mind. Engines, transmissions are all designed to do extremely well it that EU test, but maybe now to the detriment of real world driving. I for one cannot see how Mercedes have achieve such a jump in efficiency from the lump in my car, to the same lump in Marks car (bar more turbo boost and a lower CR) without designing the engine solely in mind to pass that EU test

 

[Dieselman]

It takes a least 30k miles to bed one in, and more.

Looking at some of the posts here, and other posters they are not terribly great, however they give a performance in terms of acceleration and top speed that a diesel engine designed 15 years ago simply couldn't achieve.

I also believe that now, more than ever, the engine is designed specifically with that test in mind. Engines, transmissions are all designed to do extremely well it that EU test, but maybe now to the detriment of real world driving.

Having had quite a number of brand new cars I can't say I've ever noticed a change in economy after the initial acclimatisation period.
I suspect economy improvements are down to drivers adjusting their driving style to suit the car.
According to the OBD Mrs DM's car delivers the same economy as it did when she got it.

I think new engines are less efficient to give lower emission readings in tests, however in normal driving this requires greater use of fuel to overcome the inefficiency.
I agree that modern direct diesel engines are giving greater output than previously, but that is mainly by finer injection and more fuel being delivered, however if just travelling with the traffic surely this greater output isn't being used, unless all traffic now accelerates more quickly, which is possible.

I filled up on Thursday evening and the tank gave 39.6mpg measured brim to brim over 627 miles.
So that's an old ultra reliable indirect sludge burner giving 20% better mpg than a new less reliable, high efficiency Cdi.
I'm really struggling to find a good reason to change.

 

[st4]

Having had quite a number of brand new cars I can't say I've ever noticed a change in economy after the initial acclimatisation period.
I suspect economy improvements are down to drivers adjusting their driving style to suit the car.
According to the OBD Mrs DM's car delivers the same economy as it did when she got it.

How long did you keep them for though? I noticed it on the last car as it was just below 30k miles when I got it, and when I sold it, it had done 7k miles. However, I started to run that car on millers eco max and noticed a massive gain after that. I've always ran the shed with it and that car has always been remarkably efficient but I got it with 44k miles, so any bedding in should have been done.

I also always make sure at least 1x per week the diesel cars I've had are given a good hard run to stop excessive "coking". I also take pleasure in seeing a little bit of black smoke from out back.

I think new engines are less efficient to give lower emission readings in tests, however in normal driving this requires greater use of fuel to overcome the inefficiency.

Never mind the heavier cars they haul around running more electrical equipment (the power to run and charge the battery comes from somewhere- the fuel you put in). However, this probably hits the nail on the head, given now with DPFs, more requirement for smaller particulate matter and mass that something gives, and its the MPG.

I agree that modern direct diesel engines are giving greater output than previously, but that is mainly by finer injection and more fuel being delivered, however if just travelling with the traffic surely this greater output isn't being used, unless all traffic now accelerates more quickly, which is possible.

Cars now certainly have the potential to accelerate quicker, and because its fun, a fair few will indulge in this. I find the turbo charger and power delivery hilarious on my car so I do use this to the detriment of my fuel economy.

Whats probably the saving grace of my car vs your car economy wise is the very tall gearing I have (39mph/1000rpm in top) meaning on legal crusing speeds, I never go above 1800rpm. Given I do a lot of A road driving and fast B road driving, that maybe explains why my returns are a lot better than everyone elses.

I filled up on Thursday evening and the tank gave 39.6mpg measured brim to brim over 627 miles.
So that's an old ultra reliable indirect sludge burner giving 20% better mpg than a new less reliable, high efficiency Cdi.
I'm really struggling to find a good reason to change.

Thats high, the only reason to change is whether you want to, not because you have to.

The way the bulk of people buy cars and finance them (and I am going OT here) forces them into a change (PCP). People buy new cars because financially they are tied into this.

Now stay with me on this one, and I know this is conjecture, but nothing sells a car faster than powerful outputs and the promise of better MPG, so they design an engine to pass the emissions test, score well on the EU tests, and out of the test parameters the engine is mapped to deliver a lot of power. How relevent is that, very, as car makers fight for your business when your 3 years is up, after 3 years, their warranty is up and the financial obligation worse case suddenly shifts from manufacturer, to customer. You're car doesn't come from that era as durability was seen as a much bigger selling point, than 1sec faster to 60.

You may be interested to read that Alfa are bring out a RWD 6pot diesel saloon and Maserati a baby quattroporte, VM Moturi will be designing and building the V6 diesel....

 

[ucr]

I have done 3600 miles in my C250CDi Sport (17 inch wheels and and 7G gearbox)

42.8 mpg Ave so far

 

[Dieselman]

How long did you keep them for though?

Normally about 60k miles or until they started giving trouble, which with the Chavalier and in particular Volvo was well below that figure.

The way the bulk of people buy cars and finance them (and I am going OT here) forces them into a change (PCP). People buy new cars because financially they are tied into this.

Now stay with me on this one, and I know this is conjecture, but nothing sells a car faster than powerful outputs and the promise of better MPG, so they design an engine to pass the emissions test, score well on the EU tests, and out of the test parameters the engine is mapped to deliver a lot of power. How relevent is that, very, as car makers fight for your business when your 3 years is up, after 3 years, their warranty is up and the financial obligation worse case suddenly shifts from manufacturer, to customer. You're car doesn't come from that era as durability was seen as a much bigger selling point, than 1sec faster to 60.

You forgot cup holders...

I agree with your thinking. Glossy brochures and cheap lease rates sell cars to easily impressed people, not any real technical advantages.

Anyone for a C63?

 

[st4]

Anyone for a C63?

Have you seen Mercedes enthusiast this month, C63 vs a C350cdi used vs new peice. Both cars once factoring in total cost breach £800pm and the C63 over 1 grand a month.

I've been out in two C63's, very fast cars yes, but far too quiet from the inside, remove some sound deadening please Mercedes.

Ps, the 211 hasn't got cup holders, I survive as I just hold the wheel with one hand and the can of juice in the other, when I am done with it, I have the facility to use the electric window and lob it out

 

[Mercy1]

My average over the 8,000 miles I have done in my C350 CDI is reading 35.5 on the OBC.
The best I have ever achieved, on an 80 miles mainly motorway trip, is 51.5 - but that was at 50 mph and I did it to see if I could! (Painful, never again). Normal driving on such a run, I have never bettered 41.5.
Having come out of an ML, I am obviously quids in at the fuel pump these days, but I generally drive to enjoy the car and I am happy to pay the price for opening up!
My satisfaction is also highlighted by the fact that our second car is a new Fiesta 1.4 auto (petrol) and the best I get out of that is 35.5, despite Ford's outlandish claims.
A far bigger worry, IMHO, is depreciation which costs us far more than fuel ever will...and I can't do much about that!

 

[@MARK]

I am reading some very odd statements in this thread and I am sure somebody has lost the plot.

Emissions and fuel economy are very different things.

Emissions is something the EU gets all flustered about where as MPG is something an owner is more concerned with. The EU does not give 2 hoots about the MPG in a particular car as long as the emissions are low.

So if fitting a DPF for example reduced emissions but also reduces economy by 5mpg then so be it. The EU hits its carbon target. So what if the motorist has to pay for more fuel which by the way means more tax as well.

Then there is the view that diesel cars must produce better MPG year on year.

At one end of the spectrum this may be the goal. Looking at cars like the new BMW 318D that can return 60mpg in real world driving you have to be impressed.

But at the other end. The 6 cylinder 3 litre engines from BMW, MB and Audi the goal is not to produce the engine with the highest MPG. It's to produce the most powerful car.

For a long time, BMW had it with the 335D at 286BHP. Then Audi came along this year with the A6 at 313BHP. In the same way MB have recently taken the C350 and gone from 231BHP to 265BHP.

You simply cannot take an engine, squeeze more power out of it and then expect to get the same if not better MPG. It doesn't work like that.

Dieselman posted

The latest Cdi give shockingly poor mpg figures.

Compared to what?

The BMW or Audi with the equivalent power output or the previous C320s or C350s that had less power output? You may as well compare it with a C250.

Unless you are comparing like with like then the above statement is just plain daft.

Then you have people moaning that they are not getting great MPG when they have bought a C350. What did they expect?

If MPG was that important to them why not buy a C200?

I don't see C63 owners complaining about MPG. I wonder why. It's shockingly bad after all. Indeed on a track you can even get it down to less than 10mpg. Outrageous???

So as always, car makers are building against regulations imposed on them. Right now emissions are top of the list, MPG is at the bottom.

So I have a C350.

Economy is not the reason I bought it just like my 335D before hand

I bought it for all that lovely torque and power. For real world performance that results in an effortless drive on any type of road. So that the car is not constantly changing down gear and reving high just to keep up with traffic.

If it then also delivers 35mpg then I see that as a bonus.

But lets get things into perspective here.

If you want huge performance AND huge MPG then you can't have it.

The more power you want, the more fuel you have to burn. That's physics right there although the fact we can now get 300bhp+ and get 35mpg+ in the same car is a huge leap forwards on what we had 10 years ago

 

[Dieselman]

Your statement is wrong on many levels, I'll answer some.

Emissions and fuel economy are very different things.

Emissions is something the EU gets all flustered about where as MPG is something an owner is more concerned with. The EU does not give 2 hoots about the MPG in a particular car as long as the emissions are low.

So if fitting a DPF for example reduced emissions but also reduces economy by 5mpg then so be it. The EU hits its carbon target.

Emissions and fuel economy are directly linked, the more fuel you burn the more Co2 you produce, so the targets are designed to reduce those emissions.
A calculation using (mpg/12.2) * 620 will give your Co2 output per 100km for diesel. Note the direct relationship between fuel burnt and Co2 output.

Then there is the view that diesel cars must produce better MPG year on year.

As stipulated in the target CO2 outputs, the reduction in available crude oil and that engineers like to make gains, not losses in technology advancements.

But at the other end. The 6 cylinder 3 litre engines from BMW, MB and Audi the goal is not to produce the engine with the highest MPG. It's to produce the most powerful car.

You simply cannot take an engine, squeeze more power out of it and then expect to get the same if not better MPG. It doesn't work like that.

Unless you make it more efficient, which is what direct injection was meant to do. no point going for it unless it does (apart from it being cheaper to produce), over an indirect engine. Who wants an engine that is dirtier less refined and uses more fuel than the previous generation?

You aren't using all the available output all the time and in general driving, which uses only a fraction of the max output, the new crop of engines is producing worse mpg figures than previous generation engines.

Compared to what?

The previous generation straight six direct and indirect engines...from the same manufacturer.

The more power you want, the more fuel you have to burn. That's physics right

It is if you are going to be lazy, but if you improve efficiency then it's not so at all.
Direct injection engines are approx 20% more efficient than indirect ones, yet we are now seeing lower economy from them. That's not right.

 

[A210AMG]

Quote...

"If you want huge performance AND huge MPG then you can't have it."

Depends what you mean by huge. My current bus does 40 to 45 mpg will probably get to 60 in 7 seconds (ish) and will do twice the speed limit and a little bit more...

Thats pretty good for a car that can carry 5 people easily plus all their luggage.

I think these newer models with the new gearbox's (7g +) so far are almost too new for any proper MPG tests from owners? Given the performance the C350cdi must offer and I would think 40mpg must be a achievable figure once some miles under the belt then the combination of peformance / ecomomy has to be pretty high on both counts.

 

[BenzedUP]

My car can get 100spg

 

[A210AMG]

^ on the right road, in the alps all the windows down and lots of nice tunnel passes to go through.

 

[@MARK]

Your statement is wrong on many levels, I'll answer some.


Emissions and fuel economy are directly linked, the more fuel you burn the more Co2 you produce, so the targets are designed to reduce those emissions.
A calculation using (mpg/12.2) * 620 will give your Co2 output per 100km for diesel. Note the direct relationship between fuel burnt and Co2 output.

But as you say, efficiency comes into it as well.

Sure if you burn less fuel, you generate less Co2 BUT if you then put a cat or DPF in the way, you end up having to burn more fuel to get the same power output but emissions (and emissions are not just Co2) fall as well

Who wants an engine that is dirtier less refined and uses more fuel than the previous generation?

A person who wants more performance!

As somebody who does not believe that global warming is totally man made and somebody who believes that regardless of what humans do, the climate is going to get warmer over the next few years anyway and somebody who knows that the melting ice caps really do not equate to rising sea levels (physics once again) I really don't care how green my engine is.

I do care how much power it has and how smooth it is though

So me the DPF is something that costs me power and stops my exhaust tail pipes from getting dirty.

the new crop of engines is producing worse mpg figures than previous generation engines.

I don't think anybody is disagreeing with you here.

At least at this end of the market though the goal seems to be about making engines with more power than the competition and not better MPG.

As I said before, with everything else being equal, to get more power you have to burn more fuel. Physics.

Sure you can try and make them more efficient and you have given the example of direct injection but such jumps in efficiency don't happen every few months so when the manufacturer wants to get more power out of an engine and hasn't got a brand new state of the art engine available (remembering that all new engines don't come along very often), economy is going to take a hit or at the very least isn't going to improve

So the jump from 231bhp to 264bhp on the C350 is a great example.

It's the same basic engine. It's been tweaked, the software has been improved, the turbo boost may have been increased and so on but there isn't any new technology in there so it stands to reason that the economy is going to be no better (and probably worse) for the 265bhp version over the 231bhp version.

I think your expectations are misplaced.

 

[st4]

DPF were introduced because of public perception of diesels being dirty due to particulates. This stemmed from inaccurate press, but the public lapped it up....they only have themselves to blame.

Of course removal of an exhaust restriction will assist performance and economy and removal of the super dose of fuel required for regeneration will help as well.

Have you read car magazine last month. They were recommending places to remove them, and get the system bypassed and the ECU mapped to take into account its no longer there.

More power for @mark, less fuel for @mark to use and more cleaning for him to do on his day off to clean the exhausts.

I'm glad I don't have one, but if you think about it, to get the same basic engine up 30bhp (whilst strangling it with a DPF) to make it sell and remain competative amongst equivilent 3litre diesel premium cars they've had to do things to make the engine less efficient, namely reduce CR and up the boost pressure and at the same.

Look at it another way, the 250cdi's here seem to be posting good MPGs and with 200bhp they are hardly slow (back it up with 369ft/lb peak torque) and they are more efficient, and with the hateful 7g box offering long gearing with a small efficient engine. I'd say that E220cdi I was loaned had the same power as your car (170bhp approx) and when driven gently (speed limits) it would give a 43mpg in the cold on a tight engine. Witha 7g thats going to be nearer 50mpg

The letter sent in response to the DPF peice was great claiming how bad particulate matter from diesels is. By nature, as you know, diesels emit more particulate matter by mass, more PM10. The real menace is PM2.5s which don't really come from diesels.

Its why cities in America (read LA) have lots of problems as they're most fueled by cars running on petrol.

The point is, the public are massively misold about diesel engines. They think the larger the EU no, EU5 and EU6 that the greener the engine is, and that sadly simply is not true due to the fuel burning DPFs these cars carry.

 

[Colin_b]

and with the hateful 7g box offering long gearing with a small efficient engine. I'd say that E220cdi I was loaned had the same power as your car (170bhp approx) and when driven gently (speed limits) it would give a 43mpg in the cold on a tight engine. Witha 7g thats going to be nearer 50mpg

Hateful 7g box? What am I missing, both my cars have this box, and I really can't fault it. I keep seeing this sort of comment, but no explanation why.