Here is the graph of all my fuel use since the truck was new on Sept 17th. I got the aerolid installed on Nov 15th so I only have two months of data of the truck naked. The goal is to determine as well as possible what the aerodynamics is doing for improved fuel economy not to set a 30 mpg run for a tank or any hypermileing stunts.
The graph shows in Red the the truck naked. I used Blue to show the winter cold weather driving period. I used Green to showcase the warmer weather driving from March on. Trips are labled. There are four dashed lines with represent composite averages of different data sets. The Purple is of the truck naked including the break in period (14.52 mpg). The Red is of the truck naked with the break in period data subtracted (16.67 mpg). The Blue is the average of the truck from new to today (17.3 mpg). The Green is of the truck with aero since Nov 15th (18.56 mpg).
If I make a statement like I achieved 30 mpg at 55 mph it is meant to be a snap shot from a read out under good conditions. By that I mean warm weather, little or no wind, and on level ground. I am not trying to make a general claim of what the truck will do as a composite average over time. For example my composite average over the last 920 miles is 18.7 mpg which is a all time high. Getting to 19 mpg in mixed driving is probably doable in warm weather and good conditions.
I currently average between 26 mpg and 29 mpg at 55 mph on level ground. I think 30 mpg would certainly be doable with a belly pan. I just do not have any long distance driving where 55 mph is the posted speed limit. I do have a trip to Deming on May 9th and a trip to Los Alamos on May 16th to check tank mpg at more or less constant speeds. If the conditions are good I may see some high returns but if windy like conditions have been through April I will not.
Trying to figure out what aero is doing in real world driving is very difficult. I am seeing a little over 10% but that is a composite average of City/Highway/Mixed. Pulling a 30 mpg average on even a pure highway trip would probably not be possible even at 55 mph with a boat tail and a belly pan. It is possible for short distances on level ground, but in the real world there will always be grade climbs, winds, traffic, etc.
I have tried to portray the truck as honestly as I can given the data I have been able to collect and to show the potential of the improvements to aero we have made. Future mods should improve the performance even more. I will try to outline that also. You all can do me a favor and stop comparing my 36 sq ft of frontal area 6K lb truck with a 365 HP engine to your Geo Metros or Diesel Jettas. It is just not germaine.