[JRMichler]

F testing: Grille block

I added plexiglas covers over the recessed fog lights. Any aerodynamic gain is small, they were added because the fog light openings filled with snow while driving in a heavy snowfall. The fogs were unuseable when I needed them the most. The fog lights on the Canyon have gaps around the edges that allow dirt, snow, and water thrown by the front wheels to get past the lights. I had to remove the original covers, fill the gaps with "foam in a can", and replace the covers. The covers were sawed to size, molded to rough shape using a heat gun in one hand and a leather glove on the other hand. I fastened them in place with 3M body molding double stick tape, then used the heat gun and leather glove to fine fit them all around.

The main grille is covered with exterior grade window film from Walmart. The exterior window film is twice as thick as the interior window film. The film currently on the truck has been there since November 2009.

The openings on either side of the front license plate are covered with masking tape. That tape has been on for over a year. I intended to replace it with plexiglas a long time ago, but laziness and procrastination won.

The only cooling air is from an opening (not visible) under the front license plate. The engine temperature has not risen from its pre-grille block values of 186 to 190 deg F, even when driving in 90 deg F weather with the AC running.

Photos are in my profile.

The reduced aero drag due to the grille block allows more and longer glides with the engine off. This is a synergistic effect, so I would expect slightly less percentage MPG gain if I had installed the grille block before the kill switch.

Results:
Winter: December 09 thru February 2010: 26.78 MPG (8.5%)
Summer 2010: 33.80 MPG (5.2%)

I speculate that the summer percentage mileage increase is less than the winter percentage increase because the engine is too lightly loaded, and spending more time in an inefficient range (less than 7 lbs MAP). Unfortunately, it does not glide well enough to use EOC to take advantage (or maybe I'm too lazy). In summer, the truck would benefit from the 3.42 optional rear axle ratio.

Added 6-12-2011: The original 3M window film is still on the truck. It got its first hole yesterday, possibly from a flying stone.

Added 7-9-2012: The original grille block is still installed, complete with the masking tape over the two smaller holes in the bumper. The engine temperature rose above the normal 188 deg F exactly once when the outside temperature was 93 F, the air conditioner running continuously, and a going up a long upgrade. The temperature on that day reached 195 F. This is well below the temperature at which the engine cooling fan clutch engages.