Quote:
Originally Posted by Skulldragger
Meh, you can say what ever you want but I know what the actual numbers show.
See, here is the thing, the Nissan was severely under powered, I used to say it didn't have the power to get out of it's own way. This lack of power amplified any problems as drag increased, causing a feedback loop. At lower speeds it was fine, but the faster you go the worse it gets. My drive to work is 25miles and almost all 70mph freeway so these numbers are correct. Your truck (you do have one and have tried this.. right?) may get better mileage because it had better aerodynamics, a better power to weight ratio, what ever but mine did not. (Man I hated that truck!)
Oh and I mean no disrespect or anything either although some say i sound like i do most of the time.
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Skulldragger,you're very correct in your assessment that things get really worse speed,and this would be in keeping with the relationship between horsepower necessary to overcome air drag varying with the cube of the velocity.
The thing about the 10-mpg figure is that,when tested at full-scale in the best and most accurate windtunnels,researchers found that the drag difference between tailgate up/tailgate down was only 1 percent.
At 70 mph it takes a 10% change in drag to produce a 6% change in MPG.
Another thing to consider is that on your 25-mile commute,by the time you get to your destination,you've just finally 'warmed-up' all your temperature-dependent systems on the truck.
Too many variables to be able to just point at the tailgate.
If you had or could make the time,you might do the 25-miles for a warmup,then get to the nearest station near the interstate,top-off the tank "completely",then do your test run.I believe you'll see remarkably different numbers.
You'll notice that many new pickup trucks have a vestigial spoiler designed right into the tailgate.The automaker did this hoping that owners would make the spoiler connection,and leave the gate 'up' for better mpg.