The tests were conducted on a normal California day, between the hours of 11:30 a.m. and 3 p.m. The sky was overcast and temperatures remained fairly consistent at 78-80 degrees Fahrenheit. The wind was relatively calm.

First in line was the Dodge, which was filled and sent out on the test with 15,155 miles on the odometer. It was equipped with a SnugLid tonneau. The Silverado was next and hit the oval with 13,646 miles on the odometer and a SnugTop Cab-Hi cap covering the bed. Finally the Ford, equipped with a SnugLid fiberglass tonneau cover, hit the track, fully tanked, with 7,998 miles on the odometer.

After doing the requisite 100 laps with the cruise control set at 45 mph, the drivers made a pit stop and were topped off per AAA procedures. The Dodge got 19.38 mpg, the Silverado scored highest at 23.06 mpg, and the Ford squeezed out 21.30 mpg.

The pit stop also included removing the SnugTop cap and SnugLid tonneaus from the vehicles. Off they went with Irwindale Speedway officials Lester Boyer, Mike Atkinson, and Joe DeFazio at the controls.

When they returned and got topped-off, the mileage was calculated. The Hemi-powered Dodge showed the most significant differential, with a 1.32-mpg drop with an empty bed, followed by the Chevy and Ford.

Incidentally, Irwindale's race central calculated that the fastest truck averaged 45.241 mph for the 100 laps, and the slowest averaged 44.496 mph.

The best mileage gains were achieved by the SnugLid tonneau-equipped Dodge Ram. The Hemi-powered truck showed a 1.3 mpg improvement at only 45 mph. The Chevy did pretty well, netting a 0.5 mpg improvement. The Ford ended up stopping a lap down from the 100 and could not be calculated correctly and there was just no time left for another set of 100 laps at 45 mph.

What did we learn? Under fairly stringent testing procedures, we quantified fuel savings as high as 1.3 mpg. And that was at a speed of only 45 mph.

We know that the results of the testing would have shown even better improvements if the baseline had been 60 mph, instead of 45. Engineers tell us that aerodynamic drag increases with the square of speed. So, even though the increase in speed from 45 to 60 mph is about 30 percent, the drag would increase exponentially to just more than 75 percent. Now, there's a whole lot more involved here than simply mitigating increased drag through the aerodynamic enhancements offered by a truck cap or tonneau cover, but the bottom line is that highly credentialed engineers will agree that a test at a higher speed would likely produce additional increases in fuel economy. They just can't assign an exact number to the gain.

SnugTop has received solid feedback from customers who have claimed increases as high as 1.5 to 2 mpg after equipping their vehicles with the company's caps and lids. This pretty much corroborates the test results.

Of course, results will vary by vehicle condition, its equipment, and the type of driving done. But, it's a safe assumption that under normal circumstances, it's possible to save hundreds of dollars annually in fuel costs by covering up that empty bed with a cap or tonneau cover.

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