I experimented with truck drafting on a stretch of open desert highway a few months ago.

The posted speed limit out here is 75 MPH. Since I've started driving the Camry Hybrid, I prefer not to go that fast.

Anyway, it's rare to find a truck tooling along much below 70 MPH out here. And the Camry Hybrid is a relatively heavy vehicle (3600 pounds or so). Consequently, I have found *no* advantage to truck drafting.

Twenty years ago, when I was younger, quicker, and more foolish, my best buddy and I drove cross-country in a Honda Civic (CVCC) sedan. It was less than 2100 pounds, right? And trucks would just pull it along. We got great gas mileage. Silly.

I just cruise at 60-65 MPH and don't bother with the trucks. And I get better mileage.

YMMV. be careful out there...

 

I personally have not tried drafting but I will be driving to FLA and back in 2 weeks. Summer 2006 I made the same trip. It was a 2660 mile round trip at 60 MPH or the speed limit, whichever was lower, with approximately 500 pounds of passengers and luggage. I got 55.7 mpg. I anticipate a similar result this time. I'm happy and don't feel the need to try drafting!!

 

Well, I am careful about taking websites as all being written by experts, or even sane people. There are websites that claim the world is flat, that Elvis is alive, and that a Klingon cloaking device was used at the grassy knoll.

I go more for experience and from observation. Experience is something one has to gain on their own. However, for observation, I would look at other vehicles and their design. Take the Prius, for an example. It has a very sloping rear profile, but at the end of the rear glass, there is a "wing". The purpose of that "wing" is to create turbulence behind the vehicle. That turbulence reduces the drag more than simply maintaining the slope, or "tear drop" profile.

If turbulence didn't work to reduced drag, I am sure that Toyota would not have put that "wing" on the design.

 

Well, going by observation, take a flock of ducks. They don't fly in a "V" formation because they all think it looks rather cool. The ducks are actually "drafting" behind the duck in from of them. They get into that "V" formation because they find the sweat spot. Now, the lead duck ends up pulling the entire flock behind him. He keeps doing that until he is tired, and then falls back. When he falls back, he can rest a bit, because he is now being pulled along, instead of doing the pulling himself.

Anyway, it would still have been nice, if Mythbusters measured the truck's fuel usage too.

 

For decades, pilots have drafted in formations to save fuel - geese have done it to save their energy since.....

Surely that's sufficent proof that drafting saves energy....and again nobody at this thread or www.cleanmpg.com is recommending close drafting.

 

I know a little about aerodynamics. Turbulent FLOW is a big drag. This is what happens when an aircraft stalls. The spoiler on a Prius is to direct the flow off the rear as opposed to an uncontrolled turbulent flow. This reduces the swirl effect. You can compress air flow easier than you can decrease it, look at the cross section of an aircraft wing.

Now for what is happening behind a truck.

1) the turbulent air coming off the back of the truck is a low pressure, this pressure equalizes with the normal air the further back you get.

2) the air mass that you are driving in begins to move in your direction, the more cars the more this happens and the farther back the effect will be felt. This is usually farther back than the turbulent flow and varies with the size and number of cars ahead.

 

I draft behind trucks at about 1 car length daily. I can't see their mirrors so i know they can't possibly see me. It's not in city traffic and I always know the route and if I don't my GPS tells me when I have to turn. I see a solid 25% gain in gas mileage. When the truck is doing 60MPH and I'm drafting I get about 59-60MPG in my 07 Civic hybrid.

 

The use of the word pulling is the problem. Bikers do the same thing - use that word. Sure the lead duck is doing more work then the rest of the flock but that doesn't necessarily mean he is doing more work then if he was by himself travelling at the same speed. Bikers will tell you they are pulling other bikers and they will also go to back to rest. When you get used to being in the back - then yes it will feel like you are pulling other bikes when you are in the front.

 

So your HCH is one of the early ones rated only at 46/51? Comparing your "25% gain in" MPG and mine, it sounds like this:

• 60 miles per hour -> 60 MPG, HCH drafting
• 60 miles per hour -> 48 MPG, HCH not drafting (not 51 MPG?)
• 60 miles per hour -> 54 MPG, 03 Prius on cruise control
• 65 miles per hour -> 52 MPG, 03 Prius on cruise control

I would have expected better performance from an HCH on the highway. You might need to ask some of the fuel efficient HCH owners on what needs to be done to improve mechanical performance. Tires too low? Oil needs changing?

Drafting also puts an extra load on the driver. Distractions like tuning the radio, changing CDs, or sipping some water becomes more difficult. It is also harder to stretch or shift positions. So for how long of a period do you draft the truck at one car length?

On the highway I typically run 2-3 hour segments and have driven 1,000 miles in 20 hours and felt fine the next day. I'll change the radio, CDs, stretch and shift in my seat or drink a beverage if thirsty. But mostly I'm relaxed, alert and find the miles pass easily.

In my state, the insurance companies raise the premiums for moving violations like following to close. So in addition to the ticket, $100, the next couple of years the insurance premiums are about $100-200 higher. Now in our part of the country, the truckers still use radios to talk to each other. Cars 'hiding' behind a truck are often talked about and the highway patrol listens to these conversations too.

Still, I wish you the best of luck with your choice. But you might want to visit CleanMPG.com for additional pointers, tips and discouragement.

Bob Wilson

 

The stretch of road that I do most of my driving has a decent number of hills and is NOT perfectly flat. Drafting behind a truck going 60-65 I get 59-60MPG. I drove non stop for over 500 miles drafting at 70MPH and it doesn't wear my out any faster than just sitting on cruise control. I also drove from Niagara falls down to orlando and tampa to kalamazoo, MI straight through without any problems just a couple weeks ago. Most of the way down I didn't draft very much but the way back I did. For the trip down I couldn't find any trucks doing 80+ so I said screw it.

Also who tunes the radio these days? Ipod is the only way to go...

I'm on my second HCH-2 and have put in a solid 20k+ miles in them. I've read over plenty of tips but I only get the EPA numbers when I really pay attention to things. When I drive "normal" I get 42-45MPG. There is a stretch of road I take a few times a week that is nice and flat that I get high 50's without any drafting or even trying. The terrain and traffic has more to do with your gas mileage than anything else. That 45 minute round trip ALWAYS gets me high 50's. The main freeway trip to work is mainly uphill 1 way and a decent amount of downhill on the way back. the downhill trip I can get high 60's but it averages out because you can't always drive downhill.