[Georgeandkira]

Ahh yes, as Ast85 says, "...with 50mph restrictions in both directions."

Smooth traffic at 45-50 = better mileage than 65-75.

I fetched my current car at 4:00 PM on Boxing Day, driving it from Bethesda, Maryland (Washington, D.C.) to Hackensack, NJ at 40-50 mph coming to a complete stop on the highway only once.
After topping off I concluded that Volvo had tweaked the engine to a miraculous level of economy.

But you can always check the weather forecasts. Clockwise rotation around high pressure systems and anti-clockwise around lows. Keep the wind at your back if your schedule is flexible enough. Ha-ha.

Also, I see I provided only 10 months of data. Sorry.