Here's my data, display vs pump mileage. Display is ~5% high. Yours sounds similar. There's supposed to be an adjustment in "engineering mode" but that's not available with the new diagnostic system. Perhaps through ForScan?
Anyone else notice that the Prius V owners report 42 MPG? It "...gets an excellent 41 mpg overall in our tests."
No mention of MPG in the C-Max write-up, just a complaint about battery size with no non-hybrid basis for comparison.
Typical CR.
Frank