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Discussion Starter #1
Took my Civic 2.2 Diesel on a round trip to Edinburgh yesterday – a 300mile round trip.

Only got 45.3 mpg on the way down and 53mpg on the way back. Weather was the same, traffic was just about the same, route was the same and I drove at the same speeds – cruise control set at 70 both ways for long periods.

Any explanations, I am baffled as to the huge difference?
 

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Wind direction and elevation perhaps, as well as time of day?
I can get a 5 - 10 difference on my daily commute when all appears the same. With a strong tail wind vs strong headwind, that difference is even greater, at least as far as I can tell.
 

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Discussion Starter #3
One was 8am (10°C) and the return 16°C at 7pm. Wind was quite calm nothing (For Scotland).

Can't expain it with the conditions and over such a long run would expected it to even out?

Thanks
 

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車神
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Maybe the car was less heavy (less fuel, you loss weight or maybe you had a poo :))
 

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無限 Unlimited
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:laugh: yeah, the car is always lighter after you've dropped the kids off in the morning
 

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Cockup Specialist
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Gradient.
Uphill in one direction and downhill return.
Under the same conditions on a flat you should get 49mpg

The only reason you use more fuel at the same constant rpm is if the load has increased ;)
Like driving with the hand brake on :D
 

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R.I.P - (User sadly passed away)
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Gradient. Uphill in one direction and downhill return.
Under the same conditions on a flat you should get 49mpg. .......
Not as daft as it might sound ...

If going North, the "ups" are steeper than the "downs", the 'CC' (which tries to hold speed \ revs constant) will use more fuel uphill than it saves downhill ...

Conversely, when going South again, the 'CC' will use less fuel uphill and save more downhill ...

On the other hand, we all know that the South of the UK sucks ! :p ...
 

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I'll go for temperature difference, plus cold engine for the start of the first run.

Have a look how temperature affects my car (Merc, but still a 2.1 4 cyl turbo diesel). This is average consumption - and the blue temperature line is recorded average temperature from the met office:

 

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Discussion Starter #10
Still doesn't explain in - weight was one person down on the way back - so 70kg makes 8 mpg average difference.
Temp isn't so much of a factor either as the mpg continues to rise even with only local commutes in colder weather. Maybe the engine was tired that day!
 

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everythings upsy daisy.
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Still doesn't explain in - weight was one person down on the way back - so 70kg makes 8 mpg average difference.
Temp isn't so much of a factor either as the mpg continues to rise even with only local commutes in colder weather. Maybe the engine was tired that day!
one way was slightly up hill check the sea level heights of both places this will either eliminate it or prove it..:eek:
 

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did u reset the trip computer before journey>

if not probably45 mpg is ** average including the previous usage????????
 

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you're in the same city as me mate,,, I get that also... it seems that from abz to edi is slightly elevated..
 
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