May 2010 issue of Car & Driver magazine has a brief article comparing the impact of various wheel diameters on acceleration and gas mileage. The test vehicle was 2010 VW Golf, so direct applicability of test results on a low HP, front wheel drive compact to a high HP rear wheel drive vehicle may be questionable. But its better than nothing.

Baseline: Stock 15x6.0" steel wheels with 195/65-15 tires = 40#:
-0-60MPH - 7.6-sec
-0-100MPH - 22.3-sec
-1/4 Mile - 15.9 @ 88 MPH
-Braking - 60-0MPH - 130-ft
-Skid Pad - 0.83G
-Fuel economy - 23.3 MPG

Plus 1: 16x7.5" alloy wheels with 205/55R-16 tires = 46#:
-0-60MPH - 7.7-sec
-0-100MPH - 22.6-sec
-1/4 Mile - 16.0 @ 87 MPH
-Braking - 60-0MPH - 133-ft
-Skid Pad - 0.85G
-Fuel economy - 22.9 MPG

Plus 2: 17x8.0" allow wheels with 225/45-17 tires = 48#:
-0-60MPH - 7.8-sec
-0-100MPH - 22.7-sec
-1/4 Mile - 16.0 @ 87 MPH
-Braking - 60-0MPH - 128-ft
-Skid Pad - 0.85G
-Fuel economy - 22.8 MPG

Plus 3: 18x8.0" alloy wheels with 225/40-18 tires = 51#:
-0-60MPH - 7.9-sec
-0-100MPH - 23.3-sec
-1/4 Mile - 16.1 @ 86 MPH
-Braking - 60-0MPH - 126-ft
-Skid Pad - 0.89G
-Fuel economy - 21.9 MPG

Plus 4: 19x8.5" allow wheels with 235/35-19 tires = 54#:
-0-60MPH - 7.9-sec
-0-100MPH - 23.4-sec
-1/4 Mile - 16.1 @ 86 MPH
-Braking - 60-0MPH - 126-ft
-Skid Pad - 0.88G
-Fuel economy - 21.1 MPG

All alloy wheels were the same model (ASA GT1). All tires were Goodyear Eagle GT.

I didn't list the noise numbers, since they are all within 1 dBA.

Gas mileage takes a big hit.

 

Interesting, I figured braking distances would have been affected more.

 

I'd be curious to see the difference in weight for each one.

 

The weight for each wheel/tire combination is shown in the post:

Plus 2: 17x8.0" allow wheels with 225/45-17 tires = 48#:

48# = 48 Pounds

 

I missed it.

 

That's the reason I haven't changed my wheels; weight!
I'm curious how some forged wheels would compare to the cast, since the biggest factor seems to be weight.

 

I would imagine that the inertia would be the directly related cause, rather than simply weight. Slightly more weight located near the center of rotation will still be easier to turn than less weight positioned further from the center. The larger the rim, the further from the center that the weight of the metal is distributed compared to just rubber/air with smaller rims.