I just completed a 4 day 2300 mile trip from New London Ct., to Milwaukee, WI., and return. I drove my 2001 Chevy S10 PU with a 2.5lt 5 speed manual transmission. The trip was made in two segments. New London to Erie, PA 540 miles, then Erie to Milwaukee, 540 miles following the same in reverse. On the first three legs of the trip the truck was empty except for two small suite casses and a cedar chest. I averaged 21mpg running at 68mph. On the last leg Erie to New London I had a 1916 Olds rear end and radiator along with a case of soda the same to suite cases and a couple more pounds. I was running right around 70mph the entire day but this time I got 22.66mpg. Why would having more weight and driving harder increase my gas milage when all else was the same?
The 1916 Olds was probably doing some of the pushing. The radiator probably just went along for the ride. Other than that, it could be
There are several potential reasons. One of which is the radiator and rear-end changed the flow of air over the bed of the pickup. Changing the flow of air over the bed will change the fuel mileage on the pickup. But odds are it’s a combination of factors. Such as the air flow over the bed, plus maybe a wind direction shift such as a tail-wind that also made your PU more efficient. It’s also possible you changed your driving style a bit such as coasting more or accelerating more slowly. I don’t think it’s any one thing but a combination of factors.
Every experiment has some “experimental error”. It’s the range of different answers due to random factors. My guess is the real meaning of your results is “no difference”.
We had this post before and concluded that unless you exactly duplictate you driving style, weather, etc., you will find a difference. The biggest difference I found was putting a roof carrier (non-streamlined) on the roof. At highway speed this thing really lowers your gas mileage.
The rear of the truck was lower. The temperature may have been higher. You washed it. Your front end alignment was in a more favorable position with less weight on the front wheels. Maybe the alignment is off and less weight made a difference. It was downhill on the way to New London and uphill to Erie. Fluke.