Those Maxxim Ahead wheels are 5 spoke with large openings between the spokes , and wider than they need to be, so yes, they'll have a negative impact on your fuel consumption.
There are a few threads on the benefits of closed / solid wheel covers.
The kind of tyres you have on them, will have more effect on MPG.
Under 17 lbs isn't all that bad though.
Going smaller / narrower / lighter will only return a profit when you can do it at very little or no cost - i.e. sell the wheels for what the replacement wheels would cost.
It's just about impossible to single out this effect in day to day driving.
You can break even on getting better / lower rolling resistance (LRR) tyres.
I've personally seen a 6.7% reduction in fuel consumption when going to the best available LRR tyres.
If you replace them when the tyres need replacing anyway, you can actually benefit from the change.