I just returned from an approx. 1400 mi. trip from KY to SC and back. I averaged approx. 900F on the pyro and hand calculated an average of 11.1 mpg. I was pulling a ~9000 lb. Coachmen TT over the Appalachian Mts. BTW, I was seeing about 600F EGT downhill and about 1200F EGT up fairly steep grades. I kept speed fairly constant from 55 - 60 mph.

I hope this is helpful to MP's scatter plot.