I've got the electric speedo/odometer set pretty accurate, but actually used Google maps to verify distance.You should see better mileage IMO, but not crazy better, maybe high teens. Are you sure you're odometer is reading mileage correctly?
Either way, I'm with Melloelky on this one - SPG are way more important MPG.
And that is a great street cam. It leaves some on the table at the top, but how it drives is what makes it such a great cam. Tick really doesn't have any duds.