<VV> OT: low-resistance tires?

[Jeff Wilson]

Okay, it's time for some new shoes for the daily driver
(modern non-vair).

The local tire store is hyping their fancy goodyear low-
rolling-resistance tires that increase your gas mileage.
Truth or fiction? 

The price difference is about $100 per set of four. 
Keep in mind I'm a 'hyper-miler' and would enjoy/appreciate 
even just a few extra MPG's. Do these REALLY make any 
measurable difference?

CJW