c350 cdi vs c350 cgi real world mpg????

[Magoo]

I would imagine that most of the people on here that ask the question about economy are the higher mileage drivers, and the 'who cares' responses normally come from low mileage drivers...... if you only do 5000 miles a year, fuel is going to be 10% of the importance to someone that does 50,000 miles a year.

I'm a low mileage driver (aprox 7,000 mls pa) but still don't mind if I'm putting fuel in a few times more a year. It wouldn't have a big bearing on the car I buy.

 

[gIzzE]

Yes petrol engines can return good economy IF you drive them carefully....however anyone knows that you can very easily half the mpg of a petrol engine if you put your foot down.

Diesels are far more consistant in the MPG range, and therefore in every day driving.

I don't think I agree with that.
I have always seen far more difference with a diesel than a petrol.


My E350cdi can drop to around 22mpg purely round town in heavy traffic, however on a run it will get 45+ sitting at 70mph all the while. That is over 100% difference.

All my petrols seem to be more like 21 round town and 35ish on a run.

 

[NISFAN]

I'm a low mileage driver (aprox 7,000 mls pa) but still don't mind if I'm putting fuel in a few times more a year. It wouldn't have a big bearing on the car I buy.

My point exactly, many private car owners clock up double what you do in a year. Therefore for a given income you can afford to burn twice as much fuel as Mr. Average. Heck if you drove my car, you would only fill up 10 times a year

 

[pjs]

I've just done 400 miles in the last few days in a (loaner) old shape 60 plate cls35ocdi. Mostly motorway at 80 - 90 and its averaged a shade under 35 mpg.

FWIW I know my c250cdi would have done about 43 mpg on the same run. ( and god, the CLS is not a sports coupe at all, nothing remotely sporting about the drive with god awful steering lock to lock)

 

[NISFAN]

I don't think I agree with that.
I have always seen far more difference with a diesel than a petrol.


My E350cdi can drop to around 22mpg purely round town in heavy traffic, however on a run it will get 45+ sitting at 70mph all the while. That is over 100% difference.

All my petrols seem to be more like 21 round town and 35ish on a run.

Little challenge for you then......

Test 1 - drive a set route (not in the city) once hard, the next time in fuel saving mode. Do this with a petrol and then a diesel car. I will place a wager that the petrol will see the biggest difference in mpg.

Test 2 - look at the manufacturers figures for urban and extra urban on a random sample of cars. Again I am sure the trend that comes out shows that petrols have the biggest difference.

Quick example as I have the E coupe brochure in front of me:

E350 petrol....Urban 29.1 Extra Urban 52.3...... urban is 55.6% of the extra urban figure

E350 Diesel.....Urban 38.7 Extra Urban 57.6........urban is 67.2% of the extra urban figure

Also have the F30 3 series brochure here

320i petrol Urban 35.8 Extra Urban 57.6...........urban is 62% of E.U. figure

320D Diesel Urban 52.3 Extra Urban 72.4............urban is 72.2% of the E.U figure


Also kind of puts that myth that diesel are poor when cold to bed too.

 

[gIzzE]

Little challenge for you then......

Test 1 - drive a set route (not in the city) once hard, the next time in fuel saving mode. Do this with a petrol and then a diesel car. I will place a wager that the petrol will see the biggest difference in mpg.

Test 2 - look at the manufacturers figures for urban and extra urban on a random sample of cars. Again I am sure the trend that comes out shows that petrols have the biggest difference.

Quick example as I have the E coupe brochure in front of me:

E350 petrol....Urban 29.1 Extra Urban 52.3...... urban is 55.6% of the extra urban figure

E350 Diesel.....Urban 38.7 Extra Urban 57.6........urban is 67.2% of the extra urban figure

Also have the F30 3 series brochure here

320i petrol Urban 35.8 Extra Urban 57.6...........urban is 62% of E.U. figure

320D Diesel Urban 52.3 Extra Urban 72.4............urban is 72.2% of the E.U figure


Also kind of puts that myth that diesel are poor when cold to bed too.

Test 1 - Done this with with loads of different cars over the years.
330i vs 330d
535d vs 335i
3.0tdi vs 3.2fsi
E320 vs E320cdi

As I said, the petrol seems to vary only slightly between the hardest of driving vs hypermiling.
Where as the diesels see massive difference between caning it and really taking it easy.

I managed 16mpg over 47 miles in my 535d while really pressing on, and I also managed 47mpg driving from Cannes to St. Tropez with 3 miles showing on the computer and no credit card that was accepted at the night time filling stations.

No matter how hard I spanked the 335i that would never drop below 18mpg on a drive, and would see 33mpg on a run if sat at 70mph.


TEST 2 - Manufactures figures? They tell me sweet FA.
Every diesel I have owned has struggled to average the urban figure, and extra urban just isn't realistic for modern driving.
Where as every petrol I have owned has got close to combined.

You say the biggest difference is always the petrol, but then you list two cars that show that is not true?


And you say 'Also kind of puts that myth that diesel are poor when cold to bed too.'

In what way??

Sorry, you lost me. You mean the official figures?

You seriously think the 320d will get 52mpg urban?

 

[NISFAN]

Test 1 - Done this with with loads of different cars over the years.
330i vs 330d
535d vs 335i
3.0tdi vs 3.2fsi
E320 vs E320cdi

As I said, the petrol seems to vary only slightly between the hardest of driving vs hypermiling.
Where as the diesels see massive difference between caning it and really taking it easy.

Totally the opposite of my experience......and quite frankly defies the laws of physics, but then again there are the exceptions to the rule

You say the biggest difference is always the petrol, but then you list two cars that show that is not true?

Perhaps you are reading things wrongly....I listed Miles per gallon figures. In the case of the MB E350 vs E350CDI, the petrol is a little over half the mpg at urban vs extra urban i.e. it uses almost twice as much fuel in the urban enviroment. The diesel uses a mere 30% more fuel.

You seriously think the 320d will get 52mpg urban?

Those are F30 auto figures and on the extended test drive I did....didn't get the impression that is was totally un-achieveable as long as you use econ mode with stop start enabled. But then again I average over 50mpg on my C class over the life of the car (2 years)...perhaps I am the STIG of fuel economic driving?

Urban is a free flowing route, many confuse that with 'city', not saying you do, but just clarifying for the sake of others reading this. I can see a city used diesel using the 'cat burn' particulate filter cleaning cycle continuously using more fuel than a petrol and totally skewing the 'normal' results.

 

[V12]

I have to agree that in my experience the diesels vary much more than petrols.
Just before i sold my clk270cdi i drove in convoy with my brother in a clk240 and we did a reset after we got off the M3 into london. I'd have to ask him what the results were, but i remember the 240 being not much worse than the 270 through london but on the M3 there was a 15mpg+ difference!

Have also compared my s320cdi to a S320 v6 petrol and found similar results.

 

[NISFAN]

You need to be careful about relying on computer figures....there is a difference in measure between the two.

As petrol engines are fitted with mass airflow sensors, and petrol engines work on a varied air flow principle (throttled air flow), the means to measure the consumption is very accurate.

Diesels do not have throttle valves or restricted air flow, they work on a varied air fuel ratio principle, so the measurement is not as accurate. They rely on injector pulse vs rpm to estimate the fuel consumption.

My own car reads a 10% lower mpg figure than my actual fuel/distance calcs, plus if I do a reset whilst on the move it defaults to around 40mpg, and builds up during the trip...often taking 70 miles before it gets to a close figure. This is common on diesel cars, but surprisingly bad on MB's

 

[V12]

Agreed, the CLK test was not scientific proof.

The S class "test" was measured from tank to tank. I ran the 320 petrol for 4 months and have now run the 320cdi for over 7 months, surely evening out any anomalies in my weekly commuting...

 

[NISFAN]

Agreed, the CLK test was not scientific proof.

The S class "test" was measured from tank to tank. I ran the 320 petrol for 4 months and have now run the 320cdi for over 7 months, surely evening out any anomalies in my weekly commuting...

Yes a much better test....do you have the figures?

 

[Dieselman]

I agree with Nisfan, a diesel engines main strength is when accelerating as it A: has more torque and B: has no throttle.

My car varies about 5mpg, town to country work. The only reason a diesel will vary more is if you then use the extra torque to accelerate the car more quickly.

 

[V12]

I know town/country isn't the same as town/motorway. BUT my s320cdi averages 45-50mpg on the motorway and 25mpg around town. I'll dig out the spreadsheet I kept for the s320 petrol although I didn't keep accurate notes of driving type/style.

 

[timskemp]

Have you looked on fully? Not many cars on there to sample but the 350 petrol can be brutal on fuel by the looks of it. Think 23 mpg vs 33 mpg and I reckon you'll be about right,

 

[NISFAN]

Have you looked on fully? Not many cars on there to sample but the 350 petrol can be brutal on fuel by the looks of it. Think 23 mpg vs 33 mpg and I reckon you'll be about right,

Interesting reading on fuelly, I looked up a few petrol/diesel cars and as I would expect found that petrols have a larger spread of mpg figures. Especially so for Turbo charged petrols like the 335i. Cheers for the heads up.

Does that prove my theory correct?.....or maybe diesels have a tighter grouping because they are driven by eco warriors? Hmmmm!

 

[rothbury]

Does that prove my theory correct?.....or maybe diesels have a tighter grouping because they are driven by eco warriors? Hmmmm!

Yes judging from the innumerable mpg threads on here I think you're absolutely right!!

 

[Deleted member 65149]

Just returned from a 180 mile drive on a mix of roads. Mainly motorway and dual carriageway, but lots of stop start driving through Bournemouth, Windsor and Slough, as well as long 5-10mph stretches caused by a couple of accidents. My C350 Sport petrol averaged 38.3 mpg without pushing speed limits too much, but also using the available power when accelerating on many occasions. I didn't think that was too shabby for an engine that still has less than 3k on the clock.

 

[Peter DLM]

Your result not at all dissimilar to my own. Nice backup

 

[gIzzE]

Right, the diesel has to go.

Someone want a nice 10 plate E350cdi estate for under £23k?!!

 

[Peter DLM]

Tipped you over the edge the has it?