make that typically "aluminum alloy" - steel is a metal alloy.
indeed, but the mileage thing is somewhat debatable. steady cruising, the weight differential makes no difference, it's only on acceleration that reduced mass means anything.
the op is more likely to notice a difference in the way the car rides because of unsprung weight as you say, but again, there's a trade-off
- steel wheels, while slightly heavier, are more springy, and thus, same tire, same vehicle, are a slightly softer ride. alloys, correspondingly, are stiffer and thus more "sporty".