[wmjinman]

Ok, gonna document what I do here, and hope to get advice/suggestions/ideas from those "in the know".

Vehicle: 2000 GMC Jimmy SUV 4-door. Previous years were called the "S-15 Jimmy", same as Chevy's "S-10 Blazer". 4.3 liter V-6 engine, 4-speed automatic overdrive transmission, 4 wheel drive & about 160,000 miles. Tires are well-worn Uniroyal Liberators from Wal-Mart. Everything is "stock".

Instrument: brand new ScanGauge II just bought.

I was in such a hurry to get started, I didn't even wait for my 2nd fillup and the ScanGauge "calibration". First off was to run a "baseline" to see what it would do at different speeds. I only did one set of passes (one northbound and one southbound) per speed over a course about 4.5 miles long. Cruise control was set going into the first (northbound) leg, then "resumed" after turning around going into the second (southbound) leg. The results follow:

Speed - - MPG - - 2nd
35 - - - 30.65
40 - - - 32.2 - - - 32.4
45 - - - 31.4
50 - - - 29.6 - *30.9 with tires over 50psi - 32.38 with tires 50+ and grille block*
55 - - - 28.35
60 - - - 26.9
65 - - - 25.5
70 - - - 24.85
75 - - - 23.7
80 - - - 22.15

* after second day testing - added for comparison*

When I was done, I did another 2-way average at 40 mph to confirm. It actually went 0.2 mpg higher than the first time.

I then went and read MetroMPG's thread on proper testing, realized that these single sets weren't exactly "statistically relavent", nevertheless, I now think I have a good idea where my best MPG will be found at (40).