This is what C/D got when it tested the 530i last year:
FUEL ECONOMY
EPA city driving: 20 mpg
EPA highway driving: 30 mpg
C/D-observed: 21 mpg

I'm getting around 21-22 on my daily commute w/ my G35c and it supposed to get 20C/29H. On 100% highway, I get around 24-25. So you're saying your 530i get over 30mpg on the freeway? Somehow, that's hard to believe because the Accord hybrid is supposed to get only around 37 highway.

Maybe you drive alot like the way they drive when they do those EPA tests. That's why you're getting those values.