S320 CDi MPG

badgolfer

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What is realistic for this car?

On long runs at 70-75 mph doing 40mpg, short runs to work (15 miles) around 33-34mpg. The computer says about 15% more than these figures but is way out.

Can I hope for more?? Anyone done better? Why is the computer so far out?

Badgolfer
 

eGuru

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I get about the same. However my computer is very accurate, checked it many times between top ups.
 

survey

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badgolfer - wouldn't it be good if MB via STAR could adjust the on-board comouter to ensure accuracy, where proven to be incorrect on a tank to tank? Mine is between 5% and 7% optimistic! Surely this cannot be beyond the abilities of MB!
 
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badgolfer

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Mine has done 2.5k now with an average of 34mpg and the computer says 39.2 so it is a long way out.

The 2 front tyres are cheapies and the cruise isnt working and this mismatch can cause problems I heard.

anyway it does the same as my wifes 2.0d litre Freelander and has almost double the power so it isnt too bad overall
 

Alex M Grieve

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What is realistic for this car?

On long runs at 70-75 mph doing 40mpg, short runs to work (15 miles) around 33-34mpg. The computer says about 15% more than these figures but is way out.

Can I hope for more?? Anyone done better? Why is the computer so far out?

Badgolfer

I measure brim to brim fuel consumption and on this model I can get 44.5 mpg on long journeys (where any time spent warming up is offset but lots of time with a warm engine in the cruise). I tend to set the cruise control @ 80 mph, which Sat Nav tells me is actually a bit less.

I have not had less than 36 mpg, even on short runs. The COMAND consumption figures tend to be a bit pessimistic in my case, but brim to brim, especially over a period of time, must be pretty accurate. :)

I think your consumption figures are pretty spot on. Other matters like driving style and tyre pressure, for example, can make a marginal difference, though with a diesel engine that will be less of a fluctuation and as you already cruise at the magic 2,000 rpm, it would be hard to improve much on your numbers. ;)
 

teabag

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I Know my S350 (3.7 litres) is a petrol engine, but over the 2,127 miles I've done since buying the car the computer indicates 26.4 MPG, I've checked this brim to brim since buying the car 4 weeks ago and found the computer to be slightly pessimistic as the actual consumption is 27.145 MPG.

I believe the computer is there to give an approximate indication of the MPG you are achieving, as in short bursts of accelleration I can see it dip to mid single figures, but I would not take this as gospel as so much depends on your driving style and traffic conditions.

Take an average over about 3,000 miles and this should give you an indication of what to expect over a lifetime of ownership.
 

teabag

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I Know my S350 (3.7 litres) is a petrol engine, but over the 2,127 miles I've done since buying the car the computer indicates 26.4 MPG, I've checked this brim to brim since buying the car 4 weeks ago and found the computer to be slightly pessimistic as the actual consumption is 27.145 MPG.

I believe the computer is there to give an approximate indication of the MPG you are achieving, as in short bursts of accelleration I can see it dip to mid single figures, but I would not take this as gospel as so much depends on your driving style and traffic conditions.

Take an average over about 3,000 miles and this should give you an indication of what to expect over a lifetime of ownership.
My previous E320CDi achieved 38 MPG over 3 years and 64,000 miles , so when you take into account the extra size and weight of the S320CDi, I think the figures you are seeing will be fairly realistic
 
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Alex M Grieve

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I've checked this brim to brim since buying the car 4 weeks ago and found the computer to be slightly pessimistic as the actual consumption is 27.145 MPG.

Take an average over about 3,000 miles and this should give you an indication of what to expect over a lifetime of ownership.

Hi Peter,

If you take as a rule of thumb that for cars of similar weight such as these the diesel will probable achieve 50% more mpg, then these numbers are spot on. I think 27.145 is a good score for a large heavy car with a 3.7 litre petrol engine. That is double what a car of similar weight and capacity would have done 30 years ago.
 

teabag

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Hi Peter,

If you take as a rule of thumb that for cars of similar weight such as these the diesel will probable achieve 50% more mpg, then these numbers are spot on. I think 27.145 is a good score for a large heavy car with a 3.7 litre petrol engine. That is double what a car of similar weight and capacity would have done 30 years ago.
Thanks Alex,
I'm ecstatic about the fuel consumption I am achieving from the 3.7

The reason I went for petrol over diesel was the general £3,000 price difference between the two models of similar age and condition; given the cost of diesel over petrol on the mileage I do and the fact that I will keep the car for 3 years, I figured to spend about £2,600 more on fuel in my 3 years of ownership.

As I based my calculations on 25MPG from the petrol engine, it was starting to look like I would be quids in, it's just a shame that petrol prices are now catching up to those of derv.
 

HelpThisDude

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My computer is also out, by a long way.
It reports, on average, that I do 62 - 67mpg, but Im really achieving 47mpg at best.
I must admit, the thought of a S320 performing so well, at 70 - 75mph, make me wonder if I can stretch to a C320 CDI for my next commuter wagon :)

In my C270 I do 390 Mile round trip to work everyday, at a very gentle 60mph from (almost) door step to work missing any hint of rush hour by a huge window.
 

BoyBlue

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Whilst I have yet to do a full to full check, on a recent drive to Scotland from Essex I managed an indicated 43 mpg. (M11, A14, A50, M6).
I found that the most economical speed was 75 mph, anything below or above this speed erroded the mpg.
Do the forumites think that low profile tyres make a difference ?
 

Alex M Grieve

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Whilst I have yet to do a full to full check, on a recent drive to Scotland from Essex I managed an indicated 43 mpg. (M11, A14, A50, M6).
I found that the most economical speed was 75 mph, anything below or above this speed erroded the mpg.
Do the forumites think that low profile tyres make a difference ?

Sounds ideal. 75 mph equates to 2,000 rpm, IIRC, just at the beginning of the plateau on the torque curve, so it should be optimum and your experience bears out the theory.
 

HelpThisDude

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Would holding a 2k rpm average, be the best target for mpg?
 

joe blake

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hi I've a 2005 s320 cri and we took it to catterick garrison and back from rainham Kent just over 600 miles total trip with high speeds 85/95 both ways and done about just over £70 in diesel very impressed for such a heavy car ...fuel was 23.9 per litre at the time
 

Craiglxviii

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hi I've a 2005 s320 cri and we took it to catterick garrison and back from rainham Kent just over 600 miles total trip with high speeds 85/95 both ways and done about just over £70 in diesel very impressed for such a heavy car ...fuel was 23.9 per litre at the time

I think you mean that you never exceeded 70mph at any point because to do so would be illegal, right? But a high average speed...? ;)

£70 at £1.239/ litre makes 56.5 litres. 600 miles using 56.5 litres makes 10.6 miles per litre. Multiply by 3.78 = 40.1mpg. Very impressive.
 

EmilysDad

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I think you mean that you never exceeded 70mph at any point because to do so would be illegal, right? But a high average speed...? ;)

£70 at £1.239/ litre makes 56.5 litres. 600 miles using 56.5 litres makes 10.6 miles per litre. Multiply by 3.78 = 40.1mpg. Very impressive.

That's a strange way to work it out :confused: I'd have converted the litres to gallons & gone from there. Where's the 3.78 come from :confused:
 

Wighty

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I think you mean that you never exceeded 70mph at any point because to do so would be illegal, right? But a high average speed...? ;)

£70 at £1.239/ litre makes 56.5 litres. 600 miles using 56.5 litres makes 10.6 miles per litre. Multiply by 3.78 = 40.1mpg. Very impressive.
Maybe he was talking Kilometers :D ....if he wasn't the A to B speed cameras will be giving him an early xmas present .
 

John Laidlaw

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600 miles = 965 kilometres /56.5 litres = 17.08 km/litre which seems highly unlikely I think ? (48.25 MPG)
1 Km/litre = 2.825 MPG.....
Could be wrong, maybe a very efficient car?
 

John Laidlaw

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That's a strange way to work it out :confused: I'd have converted the litres to gallons & gone from there. Where's the 3.78 come from :confused:
3.78 is the top hit from google and it’s wrong I think! Should be 4.55 (3.78 may be US Gallon conversion)
You’re idea is simpler, convert 56.5 litres = 12.43 gallons, 600/12.43 gets you 48.27 MPG
Still highly optimistic IMO
 

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