Indicated MPG vs Actual

[LongBaz383BHP]

Not long had my XC90 D5 and was happy to see that on average it was doing 41.6 mpg. However I found that hard to believe so did a brim to brim consumption. 465 miles = 34.6 mpg. Why would the read out be so far out. I have to say I am happy with the actual mpg as have read some far more lower figures being quoted.
Barrie

[ucb]

My V50 D5 is indicating about 45mpg and I'm getting about that, probably slightly less but within 2%

[anonymous-user]

My 2003 V70 T5 (which has many similarities to your XC90) is also wildly optimistic on the OBC. My 2008 C70 D5 however is accurate to within 0.5mpg which is probably the margin for error in exactly how much fuel I get in the tank!