Being that I've actually studied aerodynamics to some degree in college, I thought I'd chime in.

Dave - Although the decrease in drag from removing the tailgate may be part of the reason, it's probably only a VERY small part. Most likely, his faster time has to do with the decrease in weight of the entire vehicle. Tailgates simply just aren't that light.

Mechanic58 - If you don't want to benefit from the possible benefits that lowering the tailgate can afford, simply don't do it. Some people, travel ALOT! And 30 miles per tank can add up so a decent amount of money over the course of a year. So, I wouldn't go making fun of people for doing it.

All - I've read a number articles surrounding this topic. Simply put, sometimes lowering the tailgate works, sometimes not. It all depends on how the engineers designed the truck. If it was built with drag in mind, usually leaving it the way it was intended (or putting a tonneau cover) is your best result. Now, to the Porche arguement... I had learned in school that your most aerodynamic shape is a tear drop with the fat section facing forward. Nature proves this point over and over. Take a drop of water and let it freefall. Look at the shape in mid-air. Nature always creates the perfect design. Now the reason the Porche has a small coefficient of drag is that is pretty closely resembles a teardrop. Think about it.

Oh well... enough of me. I hope this was informative to you all.

David <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />