I'm not going to argue with you back and forth, but there's more than enough evidence to show that there's many people on forums, Reddit, and full length tests on YouTube of people who have hit 30's. It's really not that difficult nor is it disingenuous. The funny thing is that in many tests the B58 was only a few MPGs off your wife's B48 Mini, that's how good the B58 is given for how much more power it made. So your results lines up with what I said.
Here's a better example, the car I currently drive, I get 6-7 MPGs more than what Toyota has advertised. I push the car hard at times as well (mainly because people around in my area drive like zombies).