I was able for the first time average over 60 mpg on a trip yesterday (50 miles each way)!

Anyway, I am wondering if anyone has any tips on the best drafting techniques behind trucks. I've heard different things about how far back one needs to be. I know it'll probably depend on the speed and how big the truck is. In general, I find if I'm two-three car lengths behind it seems to make a difference but it's hard to quantify since the roads around here have slight grades on them and it's hard to tell if the MPG differences are road or air related. Anyway, I would appreciate any insights that people have regarding the best way to increase mileage!

thanks,

Aspenboy

Generally, the closer you are, the more benefit you'll get from drafting. Being several car lengths back puts you right in the "buffeting" zone of the air coming off of the truck (I think, I'm no aerodynamics expert). The one time I drafted a semi on a level interstate, I was within a car length and my instant mileage pegged out at 120 MPG.

Keep in mind -- this is not a safe practice.

Greg

'04Civic Hybrid

120 MPG? Wow, that's good. Hey, are you sure you weren't being towed by that truck?

Or maybe you have the "Batarang and cable" option?

:lol:

I will very occasionally draft behind a truck if approaching a large hill and I don't have to burn any additional fuel to catch up to his speed.

I'm not sure if this is facually correct but I picture the turbulence as a very large, very long braided rope.
The first, strongest braid intersection is about 15 feet from the rear.
Highly dangerous both to you and your car's front paint so I don't go there.

The second braid intersection I sometimes find about 30 feet back and if I am paticularly daring I'll align the rear of my car just in front of this. I'm always worried about road debris.

In the rare occasions I draft I'm in the marginally beneficial area ~50 feet back.
Since the times I do this is pulling a big hill, I'll back off as we reach the top.

Efficient drivers do it better.
1003 miles a tank personal record. 74MPG calculated. HCH1 CVT

aspenboy,
From talking with willie, the best trucks to draft behind are flatbeds without a load are best, the air flows smoothly over the top of your car if you are close enough.
Cheers,
Steven

Hidden Views Photography

Remember, folks: flocking birds typically fly in a reverse "V" pattern. That way, only the lead bird is working hard. Well, I imagine flying is hard for all of the birds, but the lead bird is the one doing most of the work, because he's got to cut "fresh air." I would imagine that they occasionally swap places, rotating the duties of "lead-bird."

Think about it, one bird in seven or eight. If the flock rotates occasionally, each bird is only spending one seventh or one eighth of his total flying time in the front. Excellent return on investment, I think!

Bicycle racers draft, too. And so do swimmers. I can vouch for the latter, I do it all the time. And I can vouch that it's EXTREMELY difficult to try to cut "fresh water" to pass your opponent when it's time to win the race.

As for driving, yeah, there are one or two "pockets" directly behind the truck. But I have also noticed that there's another "pocket" to the side and slightly rear of the big trucks, and even some of these SUVs. Heh, THAT'S really a lot of fun, drafting off of an H2. <don't mind me, I'm just playing "wing man" to your lead! >

** ADDENDUM TO MY LAST POST **

This is purely anectdotal. I need to experiment and study this highway-drafting thing further.

I had an opportunity to draft a few SUV's and trucks today. What fun! At one point, I was behind a truck-tractor (no trailor). Going about 65 miles per hour, I maintained a 2-to-3 second distance (I don't know how many feet or yards that would be).

I saw my "instant" go up about 5-10 miles per hour. This is very hard to judge, because you have to keep your eye on the road.

While drafting immediately behind that truck, a full-length tractor/trailor passed us on the left. At the point where he boxed me in and sealed off the space between himself and the "tractor-only" in front of me, I glanced at my MFD, and saw figures in the high 80's and low 90's. This continued for the entire duration of time that it took for the full-tractor/trailor to pass the tractor-only.

Then my instant figure dropped back into the 60s. Eventually, I had to pass the trailor-only for safety reasons, and after I settled back into my normal speed, I saw that my instant mileage had fallen into the mid-50's, where it typically hovers during 50-60 miles per hour driving on the highway.


Drafting big SUVs seems to offer something of a benefit, but not as much as the big tractor/trailors. Ryder and U-Haul moving vans also offer a nice opportunity; but I wouldn't follow any of them too closely, because one never knows how tired or unfamiliar somebody might be; after all, they may have been driving for hours, transporting their junk halfway across the US. :o

Bif,
If you encounter any semi's w/o gear or a flatbed..please update.
Cheers,
Steven

Hidden Views Photography