The trip computer doesn't seem that accurate to me but not consistently one way or the other.
"Percent Difference Trip 1 vs Hand calc MPG"
Negative % was when the Trip computer was low, and positive numbers when the trip computer was higher than the car was refueled and the mpg was calculated based on miles driven vs gallons consumed.
All but the first fill, the fill on the longest trip, and one other fill at a different local station were at the same gas station. I haven't traveled that far from home yet. Most were even at the exact same gasoline pump for extra consistency there, the numbers are still all over the map.
The best tank ever was with three people (technically four as the third weighed as much as two average passengers) plus overnight bags without the use of cruise control and locking the car into 6th gear manually when and where possible. That was all about steady state driving down to Cincinnati and back having to refuel on the outskirts of Toledo as the car suddenly said it wasn't going to make it back. It had only said 41.x at the time I stopped to fill, so it seems to more so underestimate the fuel efficiency on the highway, and overstate the mileage a bit in town, but that tends to shift back and forth depending on the driving conditions.