[wmjinman]

So after reading the "roof rack delete" thread, I decided to go out and try my own "A-B-A" tests. This time, instead of Washoe Valley, I went out on US-50 east of Dayton. I had work to do out that direction, anyway. So I found a pretty straight, flat, 4-lane 3.8 mile section of road with easy turn-arounds past each end, and set my cruise control for 50. First, the "A" tests, grille block still on, roof rack on:

speed - E-bound - W-bound - average
50 mph - - - 27.9 - - - 33.6 - - - 30.75
50 mph - - - 28.2 - - - 31.1 - - - 29.65
50 mph - - - 28.2 - - - 33.5 - - - 30.85
overall average - - - 30.417

I noticed the mileage was a couple mpg less than the 50 mph tests in Washoe Valley a few days ago. Two possible reasons; 1) I "calibrated" the ScanGauge between those runs and these. It estimated less fuel use than actual, so I'm guessing the mileage is lower with the new "calibrated" readings. 2) Dayton Valley is probably close to 1000 feet lower in elevation than Washoe Valley, so that should mean the air is thicker = more drag?

There was a fairly stiff breeze blowing out of the east, so I attribute the difference between eastbound and westbound to that. Without turning off the engine or the cruise control, I quickly removed the roof rack & stashed it inside, then headed back out. Four sets this time:

speed - E-bound - W-bound - average
50 mph - - - 28.6 - - - 33.1 - - - 30.85
50 mph - - - 29.1 - - - 32.8 - - - 30.95
50 mph - - - 29.0 - - - 32.5 - - - 30.75
50 mph - - - 28.7 - - - 32.8 - - - 30.75
overall average - - - 30.825

Good deal! Looks like over 4 tenths of a mpg - and I hardly ever use that roof rack. Good riddance - exept, I need to do the final "A" test. Oh, the stiff east breeze was still blowing. OK, one last "A" test with the rack back on:

speed - E-bound - W-bound - average
50 mph - - - 28.7 - - - 31.7 - - - 30.2

When added to the first set of "A" averages, we get an updated 30.3625 mpg with the roof rack on. That makes it a 0.46 mpg improvement. I like it!!

One final observation; with the newly enlarged 6.25" diameter "vent hole" in the cardboard grille block, the engine temp. stayed around 193 deg.