5.2 MPG Drove west to east at 59 MPH when I wasn't pulling 6-8% grades in 5H. 78,000# & 13'8" high. Load starts 11' behind the cab. I'm sure I coulda gotten 10 if I just had some Air Tabs.....
Haha! Airtabs would help a bit unloaded and with a lower profile load closer to the cab, that therr gap is a bit much. Installed properly, airtabs do give pretty good results in some applications such as OTR box van or reefer trailers. Low speed, frequent stop, or awkward, unaerodynamic loads will cause diminished results, may not be worth it. Of course, some rigs are just to cool, make it worth spending more on fuel to avoid those things
Drivers forget all the time.....you can't break the law of physics. It takes fuel to make horsepower and horsepower to pull whatever. An engine requires X = BTU's per cc's / stroke and the computer will feed that amount to the engine to complete the work requested ( by your foot ) to the spec output. As we move to summer blends on fuels then we will see our mileages drop. The EPA wants to remove more sulfur ( ppm content ) from your fuel as we speak. This will decay your mileage worse. We'll all be lucky to get 4 mpg soon enough. 5.2 might be bad in your mind but that's all I get all the time. JMO
......Then I turned south east and wound it up to 65 for about half the distance of the previous tankful and got 5.4. Wind is worse than grades or weight. I averaged 6.34 last year.