Mileage for a mechanical 6.5 Suburban 2500.

Been a long while since I've paid any attention to my fuel mileage with the Burb, especially, unladen. Around here, we most often have a single axle utility trailer behind us, with anywhere from a couple-hunred to 1500+ lbs on it. ~40 miles, round-trip is average. Been seeing right around 15 mpg. I've considered that as pretty good, since we are in 1st gear most of the time, out and back in, on the two-mile Goat Path, pluss, city driving in either Show Low, Taylor, Snowflake; sometimes, all three.

Well, during our trip to Phoenix and back, I had the chance to fill it up on level ground, let the nozzle click off 3 times with the same insertion. The result was 17.73 mpg. That was for close to 400 miles, with (probably) something near 1.25 hours of city driving in Phoenix and avg 60 mph of fairly mountainous driving. Is that what others who are driving mechanically pumped 6.5's experience?

With all of the "city" driving you did, it seems about right to me.
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