With the MT, I think its abt 500 rpm for every 10 mph. I know its 4000 @ 85 mph, so, 3500 @ 75, 3000 @ 65, 2500 @ 55, and 2000 @ 45. Yeah, that seems right. So, all in all, if your neck of the woods is long 2-lanes roads w/no stops, and speeds of about 55, I bet 32+ mpg is pretty easy to acheive. Its when you have 200 mi of desert separating you from everything else, and 4 hours of nothing is too much to bear. That brings down your mpgs. We stopped using the 5 for inteerstate road trips b/c of the 5MT highway speed penalty. Last trip before I got too frustrated was 1800 ft elev climb over 240 mi @ 75 mph all on cruise. Still only got 24 mpg. My Accord 2.2L 4AT would have done that @ 26 mpg cruising at 3100 rpms max, and I imagine the 5AT would be just as efficient. BUT the 5MT shines in-town. I have never consistantly pulled 22-24 mpg before the Mz5. With the A/C off, and stoplights every 1/2 mi, even with short trips avg 4 mi, it still outperforms the Accord's 19 mpg. Turn the A/C on in the summer, tho, and mpgs begin to equalize.
Traded my M-i-L for her truck 1 day and she took it 30 mi home and 30 mi back with speeds of 45/55 and the needle hadn't even moved next time I was in it.