Tomorrow I'm going to try to get my first 70 MPG trip of the year. I have done it twice since I got the car 9 years ago, the best one was 77 MPG and the second best was 71,6 MPG without modifications. But those attempts were in ideal summer circumstances, distances from 200 to 350 miles and always measured in one direction, slightly declining.
Tomorrow I have to go back, forth and a little detour for 80 miles, where I usually get ~61 MPG (63,6 MPG with only a closed grill). So it will be a challenge, considering that I will maintain speed limits and not less than 60 MPH on highways.
Mods so far:
- grill block
- tires at 40 psi
- wiper delete
- side mirror folded in
- Removed an incredible
112 pounds 
of exces weight (2 child seats, spare wheel, tools and all kind of stuff)
- I also closed the alloy rims with strong tape to see if it has really effect. If it turns out to be effective, the next step could be proper closed hubcap/rims.