Ground Effects + Springs = better MPG?

Cornering wouldn't be just for fun to drive or performance but emergency situations. Even travelling the speed limit somone / something can always jump in front of you and stopping distance or handling grip for quick maneuvers is important. If I needed to lean towards grip or mpg, grip should take priority but that's just me =). Any how I did a search there are aftermarket wheels that may provide better gas mileage:

Volk Racing CE28 Eco Drive Wheels for Prius Only! - Toyota Prius Forum : Toyota Prius Forums

10lb 16s! =). If they came in 17x6 and went from low resistance tires to high performance all seasons or summer / winter combo I think we'd have a winner and good balance of sticky rubber and good mpgs. Man I'm way off topic apologies OP.

 

I agree in general.

As for the wheels, it wouldn't likely pan out in real life. My wheels (Centerline RPM) are 15lbs-16lbs and I have LRR 215/45/17 (22lbs) tires yet I still take a huge hit in MPG. The problem is one part weight and one part rolling resistance. Wheel weight is important but no matter what you do the 17"-18" tires will always weight more than the 15" tires. So expect to add about 4-6lbs per tire. The OEM 15" wheel/tire combo is approx 32lbs depending on generation and tires. Most 17" combos are 38lbs-46lbs.

In summary, you're screwed.