[JRMichler]

This is the mod thread for my 06 GMC Canyon. The testing was A-B-CDE-F-G. I know this is not as good as proper ABA testing, but it is what was done. Mods so far include:

A: New vehicle, driving “normal”. Normal was 57 in 55 limit, 0 to 5 over in lesser limits, 65 in 65. Normal was also partial use of cruise control, maintaining speed in rolling hills, light use of brakes for speed limit changes. I did not keep gas records.
B: DWL, no longer use cruise control, engine on coasting for speed limit changes, and 55 in 55 and higher speed limits.
C: Nokian WR tires.
D: Inflated to 47 PSI (sidewall maximum).
E: Kill switch.
F: Grille block.
G: Aero topper.

A testing.

I bought the truck new with the 2.8 liter 175 hp 4 cylinder engine, crew cab, 2 WD, 3.73 rear axle ratio, locking differential, and factory trailer hitch. It was immediately equipped with a Leer model 100R topper. Tire pressure was maintained at placard (32 or 33 PSI).

Bought a Scangauge at some point. Did some experimenting with engine on coasting and found that the engine is programmed with a GMC automatic variable hot idle speed feature. The hot idle speed varied randomly from 700 Rpm to 1700 RPM. It was constant during any one coast. It would change for the next coast. Turning the AC compressor on would change the idle speed. That change would either increase or decrease the idle speed. There were times when the idle fuel flow would decrease when the AC compressor kicked on and increase when the compressor kicked off. The dealer's response: “No CEL, no problem”.

Fuel consumption was not recorded, but tank averages were about 21 MPG in winter and 27 MPG in summer. Driving was roughly 15% city and 85% highway.

To resume with a discussion of B testing...