Today I drove from Oklahoma City to Dallas and back again in the evening. On the trip back (starting with a full tank on the way back) I thought I would draft behind a truck for awhile to increase my fuel economy.
It seemed to have worked. I only really drafted half the trip back, but the trip only cost about 4/10 of a tank. I filled up again when I got back and it only required 4 gallons. It was about a 170 mile trip one way.
I know of drafting as a way of decreasing wind resistance from my cycling days, and it’s common knowledge with cyclers, and a common practice for cyclers in groups to take a turn at the front.
Here are my questions:
How much in terms of MPG is gained when one drafts behind trucks? Anyone have any hard numbers?
What distance behind trucks would be best in terms of efficacy versus safety? I stayed at approximately 1 second behind, which would be approximately 20 yards, going on average 65 MPH.
Has Mythbusters done an experiment with drafting yet?
The question of DOOM
Anyone that asks this question is never answered, as mythbusters is a siily TV program originally supported by the SDMB, but is now considered to be as silly as Art Bell and his cast of loons.
Sure, drafting a truck can improve your mpg, but it’s dangerous and, as a retired trucker, I wouldn’t tolerate it. There’s also no free lunch, so your gain is the trucks loss. It’s a very bad idea just to save a couple of bucks. When following a truck, the rule is: if you can’t see the driver’s mirrors, the driver can’t see you. Maintain a safe distance and enjoy the trip.
I keep hearing this and reading this, and I’ve never understood; issues of MY stopping time notwithstanding, what benefit do I derive from a trucker seeing me in his mirrors? It’s a freeway, what’s he going to do, slam into reverse?
That same draft that saves you MPG also will pull you under the truck and possibly to your flaming death. Watch a NASCAR race at Daytona and you will see what the draft can do.
They did runs at 100 feet behind a semi, at 50 feet, 20, 10, and 2 feet. They found that mileage imroved at each step until they got to 2 feet because (they surmised) it was too difficult to maintain the distance. At the ten foot mark they found a 39% imrovement in mpg.
They had all the usually warnings about not trying this at home and if you can’t see the mirrors, the driver can’t see you.
For anyone interested, the results:
100 feet - 11% improvement
50 ft - 20%
20 ft - 27%
10 ft - 39%
2 ft - 28%
Driving on public highways is not a competitive sport. It requires attention to detail, courtesy and common sense. If you can’t figure out why anyone, including truckers, don’t like being tailgated, then your not much as a driver and I’d guess that you would want to argue w/ any explanation I offered.
Done on Mythbusters. Saves gas but is very dangerous. One other thing that might have saved you gas is slower speed.
I guess if there was a headwind *and *you stayed alert and almost the recommended distance, it could save a tad, more or less safely.
But otherwise too damn dangerous.
Nametag: he knows you are there, which is important if he has to stop of change lanes. It’s the being behind and to one side but still in the blind spot that is really fucking dangerous.
On re-reading that came off as harsh. The pocket of air that allows you to save gas also can pull you into the truck. Seeing the driver’s mirrors allows him to know where you are. If the driver has to change lanes or slow down, he knows you are there. When I drove truck, I used to try to memorize the vehicles behind me. If I couldn’t see one, I would assume that there was another that I also did not see.
One big saving that comes from tailgating a truck is that most truckers keep a constant and sensible speed and, by following them, you do the same. Of course, you can do that without putting you and a trucker at risk all by yourself. Cruise Control might help with this depending on your car and the road. If your CC is messing too much with the throttle (cheap cars or hilly roads), it might not give you too much of a saving. In this more than in any other topic, YMMV
[QUOTE]
“In effect, the vacuum shadow becomes longer and more turbulent for the lead vehicle, costing it mileage (or in NASCAR situations, top speed).”
Being one second behind any vehicle just is not advised. Is better gas mileage worth your life? What if something goes wrong and the trucker has to make a sudden stop, looks in his mirrors and sees no one and begins to slow down? Well, hopefully you react in time, but since you’re about four times as close to the truck as you are advised to be when driving on the interstate, you may not react quickly enough.
Maybe you’re the best driver in the world though, and have nothing to fear. Personally I wouldn’t risk it, it’s just way too easy to break concentration for a split second. On the interstate, when moving at speeds of 65 mph +, I always try to avoid clumps of vehicles and have a good deal of room behind and in front of me, that way worst case scenario I can probably lock up my breaks and veer off the road if it looks like something insane is going on in front of me.
I once had a car about 100 yards in front of me spin out with no warning whatsoever and if not for a few inches we’d have collided with me going around 70 mph–I’d rather not find out what that feels like.
Enjoy those savings in fuel $, and be sure to keep track of them. That way, when a piece of retread comes loose and you have no opportunity to avoid it, the net cost can be accurately calculated. :rolleyes:
Yes, I have a feeling that the expected savings from drafting off of a truck is negative, due to black swan events such as being hit by debris or rear-ending the truck.
I realize that this is, in theory, verygood advice.
But you try it on a busy interstate like the New Jersey Turnpike and see how you go. Leave more than about one and a half car lengths between you and the guy in front, and within ten seconds some asshole will slot into the gap.
And as for tailgating, i long ago came to the conclusion that trucks must gain some benefit from tailgating cars, given how often it happens on the freeway.
Yes, I KNOW why the TRUCKER doesn’t like it, and I KNOW why following too closely is dangerous. Answer the question I actually asked – why is “the trucker can’t see you” presented as a compelling argument in that situation?