Google maps says 215 miles.
At 65 MPH average, thats 3.5 hours. At 55 MPH average you would still be under 4 hours and at 52 MPH you would still be under 4.25 hours.
A ScanGauge would really help. Your sweet spot for economy is probably gonna be close to 40 or 50 MPH. Then it's a matter of how much speed you want to gain and how much mileage you're will to trade off for that.
The worst thing is carrying speed over hills with anything this large.
I don't doubt that with a lower average and letting speed bleed up the hills and picking it back up after you're downhilling that you couldn't exceed 20 by a good chunk.
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