Mythbusters had an interesting episode this week where they measured fuel consumption decreases when drafting a tractor trailer from 100, 50, 10, and 2 (!) feet. The results were up to a 50% decrease in consumption.

Now it is of course mentally insane to draft a truck at 2 feet (actually 10 feet had the best results), but even 100 feet had a significant (I think it was around 20%) decrease in fuel consumption.

The truck and car were traveling at 55mph, so one would assume that at 65mph, the same results would be achievable at a slightly further distance.

FYI, for all you hyper-milers.

Interesting that they also showed in the same episode what can happen to you when a truck tire explodes at speed and the rubber belts come back at you!

So admit it! Do you follow trucks un-safely close?

Personally, I would be worried about stones, etc.

Update: The episode is called Big Rig Myths, and is on again on 10 June @ 7pm and 11pm ET.

 

I've followed trucks (not as close as 10 feet though) never wholeheartedly believing it was helping. I had seen the MythBuster episode where they tested fuel consumption on a pickup truck with the hatch up or down, and was wondering if they would ever test drafting. Thanks for posting!

...and yes...stones from trucks have chipped windshields on several of my cars sometimes more than once.

 

If you get close enough, you might actually be protected from paint and windshield chips.

I did a fair amount of drafting during my Denver-Dallas-Denver trip last month. Of course, I have paint protection film covering the entire front of my car. A lot of the trip was with strong crosswinds and I found that driving alone at 60 mph yielded better FE than drafting at 70-75 mph.

 

Those of you that have ever drafted a truck on a motorcycle would know not to make a habit of it, unless you also happen to wash your car with sandpaper (and add sand to your washer fluid to help scrub off the bugs).

 

Droid13,

I agree, but the 100 ft distance with the (I think it was) 20% decrease in fuel consumption, does sound a little tempting.

 

Sounds like an interesting test. However, as I remember, the reaction time and braking distance result in a stopping distance much greater than 100 ft.

Sooooo a 30 to 50 percent increase in mileage will relate to an 85% of death during an emergency situation.

.... I'll pay for the gas, thanks!

 

Drafting is used on race track all the time, to follow lead car and have fresh engine power later. At some particular distance (depending on the speed) you get the different effect, where the air streams meet again and you can get nice buffeting which probably would lower fuel consumption. I've been using drafting since I was a kid, you have no idea how much faster you can go on racing bicycle following bus, if you go close enough there is no wind at all and you can probably go more than 40 mph without much effort.
It is dangerous following other cars very close, but at very close distance the impact actually could be much less, because there is not enough time for the car in front of you to slow down much before you crash into it and it's not how fast you're going but the difference in speed that makes the difference, so unless you manage to somehow go under a truck or totally loose control of the car and wipe out, actually following the truck few feet behind may not be that serious, ending in some equivalent of 5-10 mph fender bender but at the same time is much more likely. Since air resistance goes quadruple every time you double the speed I would imagine fuel savings would be much, much greater at higher speeds, lets say 90mph as compared to 55 as tested.

 

There are so many variables.
It seems to me that many times I or a truck merges and I end up about 30' behind him that the TCH and my previous Maxima both suffer with buffeting (i.e. feels like the steering wheel is being moved 2" back and forth).
Apart from any dangers there's the fact few trucks are able to maintain a constant speed slight hills can slow a large truck up to 10mph which will obviously hurt FE.

 

Wow,I would have never guessed that you could still get a 20% increase at 100 feet.The old rule of thumb was 1 car length per 10 mph??100 feet is about 6 car lengths? I don't know;at 65 mph you cover that 100 feet in 1 second.Of course, the truck can't go from 65-0mph very quickly, or in a short distance.I would guess it would take a truck at least 250 feet of actual braking to stop at 65mph.A very good car could stop with 140 feet of actual braking at 65mph.
If you are a very adept,alert driver, then 100-20 feet is probably safe, but not as safe as 150feet of course.
Tempting.I frequently follow trucks at night ,letting them light the way,and show me the bends in the road,slow drivers ,cops, knock big debris out of the way(couches) etc.I follow at 200-400 feet;I don't think I would care to follow at 100 feet-certainly not at night.
Something to think about, but one windshield chip can be $300-(100 gallons),so I will probably pass on it.
Thanks,
Charlie

 

It 's not the quick stop that's gonna get you from tailgating. Did anyone see what the tire debree did at only 40 mph? Decapitation doesn't not sound very tempting to me.