Something I have always thought helped improve your MPG was to get into the draft of a semi. Does anybody have any proof, evidence, or number that might prove or disprove this theory? I have always wondered.

It does seem to increase the vehicle's response to crosswinds. That or there is a degree of buffeting from the sides generated from the slipstream you are in.

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'98 SC XLT 4.2
4x2 3.55 ls
Gibson 3" cat back
K&N filter (who doesn't?)
Cpt. chairs, and those oh so cool auto headlights.
Factory door steps to get my pants dirty

 

You would get a Big benefit from a draft. It would be like driving with a 60 mph tail wind.

 

Well I tried to apply this theory while walking down the hall at my work place. It didn't work! But I got to tell you, you do not want to be in my draft, PU

I did this one time with my car I think (not on purpose). It felt weird, I mean it was as if I was being pulled left to right? Does this mean I was drafting?

But then again the rocks that the trailer throws at you are not worth the little extra MPG you would get!




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sounds like a good way to upset a semi driver, and thats probably not a good thing

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2001 F-150 XL SWB
4.2L 5-spd, 3.55

 

Turtle? Any views on this LOL

 

I dont have any stats on this. I can only say that I tried to do that with my 95 F-150 4.9L. My engine heated up real bad. Probably because I wasn't getting enough air through my radiator. Other then that it was effortless on the engine. It had to be getting better mpg. My 2000 never heats up, so it just may work. I don't realy travel the highway much. If you do, that would probably be a great way to shave off some money at the gas pump. Most of those guys go to slow for me to want to be behind them. That, and I can't see a damn thing.

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2000 F-150 2wd sport 4.2 V6
XLT, Ext cab, auto transmission

(Performance)
JBA Headers:Jacobs Ignition:K&N:Superchip
Throttle body spacer: Cat back exaust
4.10 gears (had 3.55)

(Appearance)
AR 17x10 Atlas Wheels
Custom Seat Covers: Dash Mat
Floor Mats: Cd player: Pioneer Speakers
Rockford Amp: Truck box: Rhino Liner
Grill Guard: Nerf Bars: Fender flares
Custom graphics: Euro Tail lights
Vent Visors: Driving Lights
Tinted windows
3 inch spindle lift: 3 inch body lift: lift lips
33/12.5/17 Procomp A/T

 

DON'T DO IT !!! It's called tailgating and it's illegal. It's bad enough a professional driver has to deal with morons in front of him/her, they don't need any behind them. The last thing they need or want is an accident involving you ! The few times I've driven a semi (spared) it was suggested to "accidently" let my trailer tires swerve and kick up some stones to get rid of the dope ! Better a good scare or a chipped windshield rather than you getting killed. If you really want to save gas then get your truck hauled on the semi !

 

If I were you, I wouldn't be up on a semi's tail even if you were getting a little help with your mpg. Minus the downside of getting everything from the road thrown at your truck you'll either get pulled over by the cops or you'll end up kissing the back of the semi if he's got to stop. Better safe than sorry.


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1998 F-150 Black & Silverfrost
4.2L V6
extended cab, short bed
5 speed manual
3.55 limited slip

Performance:
Ravin Z55 exhaust SI/SO
K&N airfilter

Accessories:
Extang snap bedcover
Bedliner
Clifford alarm
Window tint

 

I've done it on a trip to FL in a conversion van. I had a CB and asked the truckers if they minded if I got in between them and we cruised! We were going about 75 mph and I definitely picked up an extra 5-6 mpg. On the otherhand, I've driven an RV and when cars get behind you, you can feel them dragging you down making your mileage worse.

 

DougH- Not to discount what you said, but the lead vehicle will also benefit from being drafted (you many have felt something different). The trailing vehicle will decrease the pressure drag on the back of the front car, therfore making it easier for the lead car. The trailing cas gains the most mpg because it no longer has to cut through the wind.

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My first Baby:
2000 SC XLT Bright Red, 4.2L, 5speed, K&N air filter, 3" intake mod, 16" perma cool electric fan, Jacobs DIS, best 1/4 mile: 17.1 @ 81.53 MPH

My Second (but most important) Baby:
Hailey Jean, born April 9, 2000

 

I didn't mean tailgating in the strictest sense of the word. You can feel that you are in a semi's slipstream pretty far behind him, and so long as you can see his mirrors... Kicked up rocks would be the worst thing, that and if he blows a tire.

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'98 SC XLT 4.2
4x2 3.55 ls
Gibson 3" cat back
K&N filter (who doesn't?)
Cpt. chairs, and those oh so cool auto headlights.
Factory door steps to get my pants dirty
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'01 VW Jetta TDI

 

Itmox said:
Something I have always thought helped improve your MPG was to get into the draft of a semi. Does anybody have any proof, evidence, or number that might prove or disprove this theory?
__________________________________________
There has been great discussion on this phenomenom. There is even a name given to people who do this sort of drafting. They are called "organ donors."

 

OK, so maybe a little more clarity is needed here. Were not talking about crawling inside someone's tailpipe here, it's more like 4,5,6 car lengths behind. A semi displaces a substantial amount of air, and you don't have to tailgate him/her to draft.

Most of the highway travel I do is on roads with high volume, like:
90/94 between Chicago and Madison, WI
35 between Dallas and S.A.
Anywhere on I-80.

So whether your going 65 behind a semi, or going 75-80 changing lanes, passing cars and then tailgating cruise control happy geriatric raisins that are going 65.2 passing that semi, it will always be a little dangerous. It just seems that taking it easy a safe distance behind a truck, but still borrowing his vacuum is the way to go. Which leads me back to the original question...

I'd like to see 22-23 mpg out my truck maybe. Or maybe 60 out of my Diesel VW.


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'98 SC XLT 4.2
4x2 3.55 ls
Gibson 3" cat back
K&N filter (who doesn't?)
Cpt. chairs, and those oh so cool auto headlights.
Factory door steps to get my pants dirty
----------------------
'01 VW Jetta TDI

 

Just remember, when following a semi, if you can't see his mirrors, he can't see you. Frankly, I feel safer in knowing that the semi driver is aware of my following him. Also, I don't think you want to be too close when a semi blows one it's recaps, as evidenced by the large pieces of tire treads you see all over the roadways.