Yes, the domed stainless steel wheel covers creak like crazy, and eventually, they may start to fall off; depending on the state of the roads you frequent. The right front is the most likely to end up on the shoulder and the right rear then may fall off, as well.
If you still have the stock plastic wheel covers, you can pop rivet 16" aluminum pizza pans (coupe style) and get better FE and hopefully not lose them...
Amazon.com: Winware Coupe Style Aluminum 16-Inch Pizza Tray: Kitchen & Dining
What are you RPM's at say 65mph? You might be able to get taller tires with a larger outside diameter and essentially raise the gear ratio; though you will also have to calibrate your odometer readings for accurate MPG's.