I agree with Rigger, it sounds like you guys are doing a great job with the MPG's.

The 5-speed having lean burn is probably the biggest reason for it's MPG advantage.
The CVT is an efficient design, but still has more losses than the manual transmission.
I also hear that the charging scheme on the CVT is different from the manual, as in it's harder to pull the battery pack's state of charge down with the CVT.

And as everyone says, the driver has the largest impact on fuel economy.

Regards,