[ImperialCrown]

You would probably not notice any real difference in day-to-day fuel economy or handling with aluminum over steel wheels. A half inch narrower width should still work OK.

 

[valiant67]

The narrower tire and lighter rotating mass would improve fuel economy and less unsprung weight would improve handling. But on a vehicle like a minivan, the effects would probably be too small to notice as stated above.

 

[Stratuscaster]

For what it's worth, the 16" alloy wheels from my departed '99 Grand Caravan replaced the 15" steel wheels on my '02 Caravan - primarily because the tires on them were less than a year/10000 miles old. Not the same scenario, but I noticed no adverse effect to handling or MPG.

 

[TWX]

I know it's not the same vehicle as yours, but when I switched from 14" steel wheels with stock tires to 15" aluminum wheels with stock tires for the 15" application on my Stratus it made no functional difference.

When I went from 15x5.5 or 15x6 (don't remember which) steel wheels with skinny 205/75/15 tires on the '79 Cordoba that I had for awhile to 255/60/15 tires on 15x7 aluminum wheels it also made no functional difference in fuel economy.

 

[Stratuscaster]

But - when I put wider 205s on my 14" steels on the Stratus, it wanted to follow every crack and groove in the pavement. When I went back to 195s, that problem went away. But I digress.