I filled up last night and this tank was the first tank with the tires pumped up to 45 PSI. I originally had them at 30 PSI. This is my 4th fillup this month, and the others have been around 41-42 MPG. For the tank the only thing that changed was the tire pressure, and I managed 45 MPG. Thats about 3 MPG, or 7%.
I think I can do a little better on the next tank, as 50 miles of this tank were still on 30 PSI. No driving techniques or modifications on this tank. I have one rule, speed limit is 60 mph. I'm going to do a couple more tanks at 44 PSI, then a few at 60 PSI to see what effect it has. By that time I should be ready for my alternator delete (almost done, just need the battery) and power steering delete. With those mods I hope to be around 50 MPG without any advanced driving techniques or aero mods.
Update 8/20/2013
3 tank average at 30 PSI = 41.4 MPG
5 tank average at 45 PSi = 45.4 MPG
(4 / 41.4) x 100 = 9.6 % gain
