How accurate is the mgp fuel computer as did a 200 mile round trip today, mainly motorway sat at 70, bit stop / start on way home as rush hour traffic averaged 22.9mpg in the supercharged according to the computer, if that's correct then I'm very pleased. Reset the computer just as I left by the way.

According to my info and experience at least 10% of the actual consumption. In my case the computer was more positive than real life but since I don't pay for the fuel, don't really care  MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

Fill the tank to the brim and take a note of the mileage (A) Drive around then brim the tank and keep note of litres used (B) to fill next take note of the mileage (C)

Subtract (A) from (C) = miles covered = (D)
Divide (B) by 4.546 and take note of answer (E)
Divide (D) by (E) = your fuel consumption


Alternatively click here and fill in the boxes

Use fuelly.com

End of. Land Rover Addict
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2009 5.0V8SC Autobiography
2006 4.2V8SC Autobiography
2004 4.4V8 Vogue

My computer hits 20+ on the motorway quite often, a bit of spirited town driving soon sorts that out though .... 
07 Supercharged - Still breaking her in!

Boot soundproofing part 1 - http://www.fullfatrr.com/forum/topic15612.html
Custom exhaust - http://www.fullfatrr.com/forum/topic15296.html
18" wheels for Brembo equipped cars - http://www.fullfatrr.com/forum/topic15052.html

I find it pretty accurate. I did about 1000 miles with brimmed tanks and the computer showed aprox 26mpg when my actual paper calculations showed aprox 25mpg. I have done similar on a coupe of occasions with similar results. So, my conclusion is that it's slightly optimistic but fairly accurate. No longer FF owner but still interested. Present car Jaguar XE
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Previous car Td6 SE
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Previous LR- Disco 300TDi Auto

My OBC has been spot on when compared to fuelly mpg for the last three fills.

Filled up tonight, did 20 miles at mixed speed limits and got up to 29 mpg (sawed right foot off and replaced with bunch of feathers)  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

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