Insight wheels are also a pound lighter than HX, for what it's worth - I have both.
(not my car)
The only RE92's that are LRR are the 165/65r14's. In the 185 size I believe you're going to want Michelin Energy Savers, which aren't quite as LRR but have something like 2-3x the tread life.
Block that grille, put a belly pan or air dam on it, and fill your tires up. Add an engine kill switch and if you're feeling adventurous, an alternator kill + deep cycle battery (so you can still turn the alternator back on if you need it), and you should be able to surpass your goal.