Tailgate up or down? The television show Mythbusters is sometimes interesting, sometimes silly but I caught one yesterday addressing this “what everyone knows” advice.
The often repeated premise is that an open pickup truck bed is bad for gas mileage because it catches the air and creates drag, so the easy, zero cost method for increasing mileage by reducing drag is to drive with the tailgate down thereby letting the air escape. Seems logical, right?
The two hosts drove two Ford F150s, as identical as possible, filled up with identical amounts of gas, one tailgate up, one down, until they ran out of gas. Driving one behind the other, you guessed it, tailgate down went dry first! The tailgate up truck went 30 miles further. Hmm …
Searching for an explanation they built a fluid flow simulation of a wind tunnel with a model truck. The answer lies in the fact that an open bed with a closed tailgate creates a rotating bubble of air in the bed that remains trapped there. Air coming over the top of the cab is kept out of the bed by this bubble and drops down behind the truck. Open the tailgate, the bubble disappears and air over the cab drops down faster, hitting the bed and creating drag. This explanation agrees with designers from the auto manufacturers who say the same thing. Who knew? They didn’t address the bed cover or no bed cover question which I presume will be coming up next season.
This falls into the “I-thought-so” department for me. As anyone that has ever ridden in the back of a pickup can attest, as I have and can (this was back when it wasn’t considered child endangerment), there is quite a back draft there.
As to the bed cover, I remember reading a test somewhere that showed that I half cover (covering the back half) was ever so slightly better (!) than a full tonneau cover and that both were definitely better than none at all.
Good evening,
My son is doing a science report on weather it is better to drive with a tailgate up or down. If you can provide us with any scientific information in regard to this matter it would help us greatly. We thank you for your time.
Sincerely,
Jul
stararealtor@comcast.net
Sounds like your son should be doing the research and work and perhaps that information will help HIM out greatly, not “us”
I have done my own research on this with 2 different trucks over the past 3 years. With the limited space to respond here, there is a critical speed in which gas saving actually occurs. Believe me when I tell you this… if you have a long haul, and set your cruise control at 65 or 70 you will see a 3 mpg increase with your tailgate down. I found NO difference with it up or down at 55 or 60 mph. Air is a fluid and velocity has a great effect on how a fluid creates drag. Just stick you hand out the window at 50 , 60, and 70mph it will make sense.
In addition to NOT improving mileage at higher speeds air is drawn under the open tailgate and the truck itself creating lift and compromising rear traction and control. The open tailgate also becomes a paticular hazard in the event of a rear end collision involving a lower riding vehicle such as a car making the practice even less safe.
Is this the same Craig Marckwardt that worked at American Honda in Gardena, CA in the late 1970″s?
I understand the comments re open vs closed talgates. What about removing the talgate altogether ?