Haha, why should I mind that, its your car your choice.
So what's the difference?
I'm getting same fuel economy at 5w50 that you're getting.
5w50 gives way lesser friction as compare to 5w20 or 5w30.
I would say choose oil that suits you, your driving style, and the places you're gonna drive.
Btw fuel economy difference in 1.8 with ac and without ac isn't much like its in decimal figure.