OK - next test. On a relatively flat stretch of highway (rolling hills are ok as long as up and down are roughly equal) reset one of your trip odometers and watch the average MPG vs. average speed. Report distance, speed, and mpg numbers in both directions on this stretch of road please. What I'm looking for here is to see if your car is performing properly on the highway.
Sorry for the delay, but life sometimes gets in the way... here are the test results.
Test course – US 421 between Windy Gap and Yadkinville NC
Sunday, 10/2/16; 1:45 – 2:15 PM @81 degrees (A/C on for all tests)
Tire pressures: RF 42; LF 41; RR 42; LR 43
Cruise control set to 55 mph
RPM average 1500 – 1600
52.5 mpg @ 6 mi – 55.1 average speed
Cruise control set to 65 mph
RPM average 1800
46.0 mpg @ 5.4 miles - 65.4 average speed
Cruise control set to 70 mph
RPM average 2000
35.3 mpg @ 10.6 miles - 69.5 average speed
34.5 mpg @ 12 miles - 69.7 average speed (continued from above test)
No cruise control
42.3 mpg @ 6 miles - 68.9 average speed
40.9 mpg @ 7.2 miles - 66.1 average speed (continued from above test, includes going from US 421 to I-77)
36.5 mpg @ 6.3 miles - 73.2 average speed (Test on I-77 N)
Since the test, I've had a flat, (wore out the inside edge of the tire, but the alignment #s didn't show anything really out of whack... very strange.) got all new tires (Continental Pure Contacts), front end alignment, had the HVAC flashed to fix the hum issue and had the LTFT reset. We'll see if there is a difference. I also ran a tank of B18 through it before I got the flat as I wanted the detergent properties of the bio to make sure everything was "cleaned out" so to speak. Now I'm back on regular diesel from Sheetz. We'll see what happens...