I gather these 'cruising' mpg comparison comments are just OBC readings.
There can be quite a bit or error if taken from the OBC, unless you are checking accuracy by 'brim to brim' calcs. Say there is a +/- error of up to 10% (that is possible against actual consumption) could be a 10mpg difference in OBC figures between two cars, even if all other things were equal at around 70mph. Most unlikely the other factors are equal either.
HighlandPete
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