Assuming you have the correct size of tyres fitted to your 20" wheels there should be no difference in the rolling circumference versus the 18" wheels. Therefore, your ECU won't 'know' that you have made any change.
However, increased rolling resistance could reduce the fuel economy and this could be shown on the display.The older I get, the more I realise that people confuse wrinkles for wisdom
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10th Sep 2009 11:02 pm
01coccobet
Member Since: 23 Feb 2009
Location: on air
Posts: 2624
It's common that you experience an increase in fuel consumption due to' the increased wheight and size(ie rolling resistence)figuring it out!!!!
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10th Sep 2009 11:05 pm
al cope
Member Since: 08 Nov 2005
Location: Oldbury, WM
Posts: 10303
if you gone up in size (not a directly equal tyre size - something like 255/60x18 to 275/45x20)), then your actual MPG might be slightly improved, as the tyre is covering slightly more distance for each turn, buts its fractional, so dont worry about it.
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11th Sep 2009 9:46 am
SN
Member Since: 03 Jan 2006
Location: Romiley
Posts: 13710
never worked for me with my oversized ST's - 1% greater rolling cicumference generating 10% reduction in mpg Steve N | 21MY Defender | 08MY Discovery 3 (history) | 06MY Discovery 3 (ancient history)
11th Sep 2009 10:09 am
DaveVX
Member Since: 15 Oct 2008
Location: Hampshire
Posts: 867
just wondered if it had an effect couldnt get my head around it.
Might be getting less mpg but that may be to do with heavy right foot
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