Highway @ 75mph

If you want to maintain an average of 75mph for the trip, here are things you can do to improve mpg:
1. Increase tire pressure. Going from 35 to 45 will net you a few mpg. Research and understand the effects on noise and handling when doing so!
2. Use the "driving with load" hypermiling technique: see #56 100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com
3. Low rolling resistance tires if not already installed. Best are Michelin Energy Saver A/S followed by Bridgestone Ecopia EP422.
4. Partial grill block - Improves aerodynamics
5. Purchase a Scanguage to track fuel economy on each drive, allowing you to experiment and see what works and doesn't work.
6. Other aero mods: 65+ Vehicle modifications for better fuel economy - EcoModder.com

I have good luck using a Scanguage on my current interstate commute and using cruise control where relatively flat. I turn it off for hills and use a minimum rpm of 1400 and a maximum of 3500. My speed varies from about 60mph at the top of the worst hill to 83mph at the bottom of the same hill, averaging ~74mph for the interstate portion of the trip and resulting in about 54mpg (58 displayed). Keep in mind I have a significant aerodynamic advantage versus the c.

 

I did not strive for 12 o'clock. But not to go higher. I strived for 10 o'clock. I was astonished with my LA-LV-LA round trip in the hot air conditioned summer, 289 miles times two in five hours each and less than 9 gallons of gas.