Hey their ucantcme,
Thank you for your great question!
This idea has been around for awhile, and I have even seen people do it to me, as well as NAFTA doing up a formal report on it, followed up later on down the road by the Mythbusters!
The truth is, yup, you can get better fuel economy by drafting in the wake of a big tuck, but their is a sweet spot where it is most efficient at somewhere around 75 to 100 yards behind a truck. That should in theory be just about right to pick up good fuel economy in at least a somewhat safe manner Of course knowing Mythbusters, they took it to extremes, and after going several rounds at different lengths, they finally got so close ( 2 Feet
) form the Magnum they were driving to the truck, that they actually started picking up the wash from under the trailer itself!
Heres a clip of their test which I got to say is pretty dang cool!
Just a couple of quick things to keep in mind though if you continue to draft big trucks.
1. Always remember that good old saying, If you can't see a trucks side rear view mirrors, he can't see you, and he ain't gonna know you are even their!
2. The next issue of following a truck for a while like you had mentioned their is a little more complicated. From a point of Safety it is not recommended! A couple of years ago, the company I was driving for had a big meeting warning us about a widespread ring of thieves that had been known to watch out for trucks picking up high dollar loads, following them, and hijack them at gun point! We were instructed to keep an eye out for any vehicles following us over long distance, especially at close distance, and report them immediately! After 9:11, we as part of our Haz Mat Certification, we had to under go training in counter terrorism directly from Homeland Security, and were given Security Badges, with explicit instructions, phone, and contact information to report any suspicious activities around a truck loaded with chemicals, or other dangerous commodity directly to Homeland Security as part of their Highway Watch Program! So don't follow too close, or get into a bad situation inadvertently, especially if you see any placards on the trailer!
Again, thanks for the great question!
Take it easy,
Candyman