MPG (makes no sense to me!)

Kinky

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Dear all,

I've been monitoring my fuel consumption from day 1, and seem to return a very regular and consistent 24.5 mpg.

This 24.5 mpg is based on the standard UL, with the gearbox running in Economy mode and with the air con switched off.

I ran a test a while ago, running the car in Standard mode and with the air con permanently on. This returned an MPG of 25.38 and 25.0 on 2 consecutive fill-ups. However, I excluded these numbers, as my routine was out of kilter during that period with lots of trips here and there.

Anyhow, I had just filled up the car, after running yet again in Standard mode with air con on permanently, and it has returned me an MPG of 25.54. This is with my usual driving routine - and is therefore 100% comparable with the 24.5mpg which I get in Economy mode with no aircon.

Can anyone explain to me why I get better fuel consumption in Standard mode AND with the air con permantly on?

I would expect less not more!

And on a side-note (to pre-empt any possible questions) - yes the E/S gearbox switch does work in that in S mode it holds the gears longer - so does work. Also the air con does work - I had it gassed at it's last service (£103) and does blow cold air when it's on (as opposed to not so when it's off).

There's also absolutely no power loss whatsoever when it's on (which has been horrendous on some cars I've had in the past.

Answers on a postcard to ....
 

Brian WH

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Surely it will depend on the type of runs? If they are lots of straight roads with no constant stop-start then standard mode will be the best choice mate. Air-con doesn't necessarily make all that difference unless it's 100F outside.
 
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Andy W

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Lower engine revs and stop starts will create more load on the engine with air con on compared to on the motorway at a constant speed and load particulary using cruise control.
 
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Kinky

Kinky

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My morning journey is always 25 miles down the M3 (away from London - so a nice quiet run - no stop starts).

My home journey varies either back up the M3 - or via the more relaxing and enjoyable A30 (1 or 2 stop starts at most on a bad day).

Very rarely use the car at the weekends for shopping, etc (have the Alfa for that - much more fun!).
 

Richard W

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Are you going to have a go with my spreadsheet?

It starts to give good results after about 3 or 4 fill ups, I tend to fill it to the brim each time and record how much is put in and the mileage at the time.

Can't explain the better results though......:confused:

R
 
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Kinky

Kinky

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Yeah - I had a look at your file today - I've got the data from 17 fill ups, since day 1. I do see what you mean by absolute nth degreee detail!

In total I've spent £616.28p, with an average cost of 74.9p which in turn gives me a cost of 14p per mile (or in real personal terms 6 pence per mile).

I'll plug my numbers into your file and see how the charts look!. In fact - I'll probably add some bits to yours which I have along with some bits I got from andrews version of the file.
 

djcheung

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Hi guys,

Before the last service ( Feb this year ), I was getting an average of 25-26mpg. I have since changed the motor oil to Castrol SLX fully synthetic oil and now the average mpg is 29-30.
I am not too sure how it affects the service intervals yet.
S/W always in the S position and aircon on whenever is necessary

By the way, mine is a 98' E240 elegance.
 

PJH

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My 280E usually gives about 29MPG.
Worst was 24.5 in Jan'03, 'cos it was v cold and the engine thermostat was u/s.
Best was a week's holiday in April when I had a best ever of 31.5 over 800 miles.

Q. Is the thermostat working correctly ?

Q. How much hotter does the engine get when the a/c is on ?

My car runs at about 84C with a/c off and 90-95 with a/c on.

When I had the thermostat replaced the engine was warmer in 2 miles than it was in 15 miles when it was u/s.

Checking MPG over a longer distance instead of just each tank will also eliminate any rounding errors.
 

kid-jensen

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Kinky,

Worse consumption in "E" mode can be explained by having to use larger throttle openings to get the thing moving (because the box is reluctant to change down).

This will usually result in more fuel being used than a lighter throttle and lower gear.

Well....it makes sence to me;)

I can only dream of these figures, I don't do any long runs at all :(
 

amdxp

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Well, first of all .................... the "S" means summer but not "standard".

The "E" means winter, it's a German word of "ice", in winter mode, the car normally start with 2nd gear. The "E" is not "economy".

MB has later changed this to "S" and "W", in English.
 

andy_k

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beg to differ on the definition of S & E

for those of us owning W124s at least the owners handbook definition of the gearbox mode selector is S=Standard and E=Economy.

I know they have changed it for the later models :)

Andy
 

GregE240

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Hmmm.

Just to add my two cents worth, I'm averaging around 29-31mpg at the moment. This is with the aircon on nearly all the time in this spate of good weather.

I'm surprised at the figures as I usually get something akin to this figure with the aircon OFF. So I think Brian has a very good point here.

The other thing I've found with my car is that in W (I have an S/W switch), the car becomes very loathed to increase speed, so you end up using a lot more right foot, hence the worse mpg you are getting?

To this end I only ever use the W setting if our road is iced up (the road inclined to the top gently), otherwise its at S.

Finally, like others I've come to the conclusion that Super Unleaded does nothing whatsoever to my engine. I don't think it increases performance, it does nothing for mpg either. I've no doubt Optimax is a good petrol in terms of its cleaning abilities, but I really do think that unless your car has been retuned for higher octane fuel (a la GDC200), or unless you want a couple of tankfuls of Optimax to give it a clean through, normal 95RON unleaded is just fine.

G
 
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Kinky

Kinky

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Just a quick update on my fuel consumption ....

Spent a week up in Yorkshire last week (week off inbetween jobs) and I managed to get 27.17 mpg at one point ! (in Standard mode with aircon on).

Overall, since the end of April, I've done a total 5,523 miles, with which I've got an overall average of 25.04 mpg.

The best I've ever had was 30.98mpg and worst was 23.04mpg.

And to compare apples with apples (ie - the handbook) - I've averaged 11.33 L/100kms, with the best being 9.12 L/100kms.

K
 

Brian WH

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K

I had an E280 1999 before this one and the mpg that you are quoting is almost exactly what I used to get, if that is any consulation mate.
 

GrahamC230K

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Stop worrying about MPG.

Once you calculated it, you can't do much about it, so why worry?!


All I know is that I have a nice yellow light to tell me I have done 299 miles, regular as clockwork.


fuel.jpg
 

sym

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350 !! before the orange light yesterday ...

woohoooooo !

S.

(No diesel owners posting 400 figures to make me feell unwell please !!)
 
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simonl

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only ~260 :(

...and the top half always seems to last longer than the bottom half. :rolleyes:
 

fuzzer

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568 Miles before my Reserve fueling visit service station symbol. ;) 615 possible :)
 
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sym

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Originally posted by fuzzer
568 Miles before my Reserve fueling visit service station symbol. ;)

in the W210, I assume . . . or did you forget to press the reset button once on the 203 ? ;)

Blimey - that is amazing !!!

S.
 

fuzzer

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Originally posted by sym
in the W210, I assume . . . or did you forget to press the reset button once on the 203 ? ;)

Blimey - that is amazing !!!

S.

Nope , my 180k will do 615 miles on a tank and the 220 CDI will do 707 on a single tank . :bannana: :bannana: :bannana:
 

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