A few people on here say the same, I have looked into it and all of them own dervs. I have worked out the average MPG on my petrol FR and it was within 2-3 MPG of what the computer said
BTW I get low 40's MPG from my petrol FR on a 300 mile round trip at 70 on the cruise, I've done the same trip a few times now and every time I get 41-43MPG