[brucepick]

I'm sure underpans would be excellent. I want to do that on my Civic but I gotta take care of the "honeydew" projects list before I can take time to do that!

An aero truck cap would probably help even more but I'm sure that's a much bigger project. Plus it might limit your load carrying ability unless you're very clever about configuring the cap to 'get out of the way' to allow oversize objects.

I'm with you re. the wheel change - -
During my last summer before becoming a committed hypermiler I changed off the 14" wheels on my then-daily driver Volvo wagon and put on 15's, with tires carefully selected to keep the speedometer accurate. Handling improved and mpg went down.
Old size: 195/75-14 New size: 205/65-15
Tires costing what they do, I'm not jumping to change them again soon. The car is semi-retired; I drive it for hauling bulky/heavy stuff and rotten weather trips. Civic for the 60-mile daily commute runs.