Cleanspeed, you post over at CAD or T-Report also? Someone else was hopped up on that formula (I read earlier today).
To the OP:
Take a truck driver tip:
Plan all your stops in advance. As fuel economy is a matter of attending to small things this would include fine motor skills. And those work best when we are rested. Relaxed. Breaking the trip into legs of about 100-miles or two hours (at most) works to this end.
I try to find both rest areas, restaurants and fuel stops on the same side of the highway. "My" side. Past any traffic stops (lights/signs) that Google Earth shows me are also fairly modern and well-kept. It does take time the first few attempts (hours) but it also teaches me some new skills. I combine with it the "adventure" from
Roadfood.com - Your Guide to Authentic Regional Eats to brighten my day for lunch. Tiny penalty, at worst, if one has checked every foot of the route away from the main road.
Time and distance calculations take more than at first seems easy. Practice makes perfect . . and when one has been doing it for years, it is enjoyable and leads to interesting diversions that can sometimes be incorporated.
All work makes Jack a dull boy sort of thing. When one drives for a living, it is the "spices" that invigorate and keep one new.
Thus, knowing ahead of time how far till the next stop -- and how long it wil take me -- keeps me focused,
allows me to focus on the here & now to aid best FE. A plan that is over-arching. Takes into account also weather, winds, traffic, construction, etc. Alternates to the days trouble can also be charted. One need not lose momentum because of the unexpected.
Buy a Road Atlas, too.
.