Does following (drafting) a semi really save gas?

[saaber1]

Have heard that following semis on the highway saves fuel. It makes sense I guess because you are in the "clean air" from behind a semi.

But wouldn't all the rocks, etc. kicked up from the semi do more damage in paint chips and damaged windshields than it would be worth in saved gas?

How much gas would it save anyway?

 

[MGregoir]

Semis are not good for cars and other passenger vehicles to draft because the air coming underneath them is basically wake turbulence and it doesn't break much air for you.

In a motorhome or larger vehicle, drafting can make a significant difference in fuel mileage or top speed.

Most cars to draft have to be within two feet of each other to feel significant effect at highway speed and that is wholly unsafe.

 

[bubbatime]

http://www.treehugger.com/files/2007/06/drafting_behind.php

 

[wagsg]

This was tested on the Mythbusters show. If I remember correctly, there is little improvement in fuel economy and you have to be dangerously close to get any benefit. Also, I believe the truckers can "feel" when someone is right up behind them... seems to change the aero feel of the truck enough that an experienced driver will notice. You don't want them brake checking you or otherwise be peeved.

Besides, it's not worth the chance of debris (not rocks, but large pieces of retread tire) coming at you.

 

[wavinwayne]

Mythbusters tested this & found that drafting behind a semi DOES save gas, but they also made a point to say that it should never be done because it's 100% unsafe.

 

[Drew99GT]

Yea, on Mythbusters, the closer they got, the more gas saved, up to the last point they did, about an inch behind the semi!

Fuel mileage increased by a ton, around 50% or more if I remember correctly, following about 2 feet behind the semi.

 

[ToyotaNSaturn]

It only makes logical sense that drafting saves fuel as the engine doesn't have to push the car thru the air resistance.

 

[wapacz]

the mythbusters had a dodge magnum if i remember right. At 100 feet they had like a 10% increase.

 

[Quattro Pete]

Originally Posted By: wagsg
Besides, it's not worth the chance of debris (not rocks, but large pieces of retread tire) coming at you.

Amen to that. I avoid driving behind a semi like a plague. That's where most of my rock chips come from. I don't care if I improve my mpg by 10% if I have to repaint my hood, bumper and replace my windshield afterwards.

 

[itchrelief]

At least in urban areas, you will generally save gas just from the fact that most semis don't break 65mph (a good half of them seem to not even reach 60), disregarding any drafting effects.

Just don't follow the gravel truck.

 

[Black Bart]

I was in the trucking business for 42 years retired now but I hated it when a car tailgated me.
I found that if I let my trailer drift over onto the shoulder and throw a few stones that got them off of my tail.
It is no fun wasting three hours filling out accident report because of some idiot that wants to draft me.

 

[leftlane]

If one of their trailer tires blows up it'll fly right at your car and that can cause a major hole in your wallet, not to mention kill you as also shown on mythbusters. Its not worth the risk.

 

[SevenBizzos]

 

[Cutehumor]

how about if I throw a hook on their bumper and hook to my front bumper. they drag my car while I'm in neutral?

 

[TylerL]

Originally Posted By: Black Bart
I was in the trucking business for 42 years retired now but I hated it when a car tailgated me.
I found that if I let my trailer drift over onto the shoulder and throw a few stones that got them off of my tail.
It is no fun wasting three hours filling out accident report because of some idiot that wants to draft me.

How close would they follow?

 

[dwendt44]

You'd have to be close enough that the truck drive could no longer see you in his mirrors in order to get any drafting effect.
Dangerous, foolish, stupid.
Accident waiting to happen.
And those are the good points.

 

[Black Bart]

Originally Posted By: TylerL
Originally Posted By: Black Bart
I was in the trucking business for 42 years retired now but I hated it when a car tailgated me.
I found that if I let my trailer drift over onto the shoulder and throw a few stones that got them off of my tail.
It is no fun wasting three hours filling out accident report because of some idiot that wants to draft me.

How close would they follow?
Some would get within 10 feet of my dock bumper but most were about 20 feet.

I could not see them in my mirrors without swinging my trailer.
On a 2 lane road many will follow close until they can pass but if they don't attempt to pass and just stay their riding my bumper for miles I became a poor driver and had trouble staying on the pavement.
When you place the outside dual on the stone that wakes them up and most of them would pass.

 

[oilyriser]

Keeping a few seconds back, you can still benefit from the wind, but it only works in still air since the wake can drifts into the other lane.

Has anyone else ever drafted in a crosswind? You don't have to be behind the truck at all...

 

[harry j]

Are some Semis equipt with rear looking cameras, like some of the new SUVs?

 

[Bror Jace]

Mythbusters proved this works ... but advised against following closely. Even at 75' there are some savings to be had.

And this is about what I do ... until the traffic gets denser and everyone is following everyone else closer. I'll also back off in bad weather ... or during the winter when the roads have a lot of little debris on them.

Truckers need to concentrate more on the traffic ahead of them and beside them (where their mishap could cost someone their life) and not worry about a compact car that might be following them a little close.