Following a tractor-trailor increase highway MPG?

<div class='quotetop'>QUOTE(brad34695 @ May 29 2007, 04:04 PM) [snapback]451714[/snapback]</div>

Yes, it does. But how much depends on the distance, and how safe also depends on the distance. If you're certain you're at a safe distance, OK. The biggest safety issue (at least for me) is visibility.

Dave M.

 

<div class='quotetop'>QUOTE(brad34695 @ May 29 2007, 06:04 PM) [snapback]451714[/snapback]</div>

I believe the term is "drafting". Yes, it will increase mpg. (Motorcyclists can tell you that it can pull the rider off the bike or they can cut the engine and maintain speed.) How close do you have to get to see improvement at highway speeds? When you are behind a tractor trailer if you can't see the side mirrors then you are not at a safe distance. I suspect that if you are at a safe distance you are too far away to draft and you are picking up the debris from the truck.

 

The bad outweighs the good. Between stones that can be kicked up and the low visibility its not worth it. Plus to find one that maintains a constant speed is difficult. I took a 520 mile trip to VA Beach from Ohio and pulled out 50 MPG

 

<div class='quotetop'>QUOTE(brad34695 @ May 29 2007, 07:04 PM) [snapback]451714[/snapback]</div>

Yes. Dragging behind a truck can make a huge difference. That's what the eye bolt is for that screws into the front bumper.

Tom

 

I drove from Denver to Dallas and back last week and did a fair amount of drafting. The entire front of my car is covered with 3M paint protection film so I'm not that concerned about rock chips (at least to the paint).

The wind was strong and out of the south on the way there and north on the way back. With a strong side wind, I found that I got better fuel economy driving by myself at 60 mph than drafting at 70+ mph. Even echeloning to the side of the truck didn't seem to help much.

 

<div class='quotetop'>QUOTE(brad34695 @ May 29 2007, 06:04 PM) [snapback]451714[/snapback]</div>

When I pull my fifth wheel trailer drafting definitly helps. I draft my friend who has a big motorhome and it really cuts down on the drag. I can drive highway speed at about 2500 RPM while drafting instead of about 3500 RPM when I am pushing the air my self.

Not sure how much difference there will be with a low coefficient of drag Prius.
Glenn

 

I draft now and then when the conditions are right.

 

I think next week's Mythbusters addresses drafting trucks.

 

I draft regularly on my 98 mile R/T commute to work. I've gone 30 or so miles at time behind the same truck and under the right conditions (speed consistency) I can average 75 MPG for the entire duration at highway speeds. Pretty amazing, but does take some concentration. I've maintained speed of 65 MPH in Warp Stealth while drafting for amazing distances.

 

<div class='quotetop'>QUOTE(Squint @ May 30 2007, 07:36 PM) [snapback]452487[/snapback]</div>

Not much to debunk really. The only way you are not going to see positive gains is if the big truck is driving erratically.

I've drafted doing 55mph and I was lucky enough to draft some going 70mph and the difference, between drafting and not, is obvious and immediate. Pull up to about 4-5 car lenghts behind a bigtruck and watch your MDF. Pull over 1-2 (if safe)lanes and watch the milage drop again. Pull back behind him and watch it go up again. You can do this 100s of times with the same reusults. While I don't personally draft very close, the effects incsrease the closer you get.

When I decide to draft, I am far enough back to be considered "follwing" not drafting.

 

I've seen chunks of tire (retreads are very common on semi trucks) come flying off, I've seen road debris become highly airborne, and I've seen what happens if you need more stopping space than you actually have....

You know, even without drafting big trucks, I'm still getting great MPG, and I have less hazards to worry about.

 

<div class='quotetop'>QUOTE(Rae Vynn @ May 31 2007, 04:24 PM) [snapback]452881[/snapback]</div>

If you calculate the savings from drafting they would takes years to cover the paint or body work required to fix one good chunk of tire hitting your car.

 

<div class='quotetop'>QUOTE(F8L @ May 31 2007, 07:39 PM) [snapback]452885[/snapback]</div>

Now that being said I would draft all the time in my wife's old Taurus and Explorer and would see significant gains, but those vehicles were already 10 years old and boxy, the prius already has the 2nd lowest drag coefficient of any production car ever built.

 

Doesn't the truck you are drafting experience a similar decrease in mileage? Seems like it would annoy them quite a bit.

 

My Uncle learned the hard way not to follow a truck too closely. The moose that suddenly appeared from under the big rig in front of him caused them to be airborne only briefly, but it was long enough.

If I'm cycling with someone I know and trust, we'll take turns drafting each other very closely, but only up to about 50kmh. Any faster than that is not worth the risk.

 

Hi...

First opportunity today to try drafting technique on a highway with new Prius.

South I880 from just south of Oakland, California to San Jose.

Pretty much flat.

Traffic moving 55 to 65 mph.

Found truck and stayed about 50' behind. When he left freeway, found another that went all the way to San Jose.

Miles per gallon (according to five consecutive 5-minute bars on display) right around 60 mpg.

Truck (along with several others) peeled off at highway 101 exit, San Jose.

No other trucks to follow... so continued on to Los Gatos on highway880/17.

This stretch has a few places where roadway dips to allow several surface streets to cross and a few places wher it rises to cross over other roads/freeways.

Miles per gallon (two consecutive 5 minute bars) dropped to just below 50 mpg.

While 'drafting' I noticed a slightly lighter touch on the accelerator was needed to maintain speed than was neccessary when I moved out from behind the truck and into the next lane.

Occaisionaly slowed to allow merging traffic between myself and the truck. Fortunately, all intervening vehicles continued merge into the next lane(s).

It could have been my imagination, but I think I could almost 'feel' where the 'sweet spot' was when I accellerated to regain my 'drafting' position behind truck.

If gas keeps going up I can just imagine seeing a Prius (or other Hybrid/EV) behind just about every truck on the longer stretches of Interstate even with the increased risk of damage from flying debris....

I really like the instant MPG displays on the Prius.

The real-time feedback provided by the displays has greatly influenced my driving habits.

Every vehicle made should come standard with a similar display, hybrid or not.

(I find the five minute 'bar graph' display more useful, and much less distracting, than the one with the constantly changing 'power flow' arrows.)

Gary...

 

<div class='quotetop'>QUOTE(NoMoShocks @ May 31 2007, 07:17 PM) [snapback]452972[/snapback]</div>

There was a rather large thread on the subject of drafting and the concensus was that the truck did not suffer for the drafting and someone reported the truck may actually benefit from it be decreasing the turbulance behind the truck. All of this will depend on how close you are and the shapre of the truck you are following I would assume.

 

<div class='quotetop'>QUOTE(garyg @ 2007 May 31 8:42 PM) [snapback]453026[/snapback]</div>

That sounds like you're getting the hang of it, though I can't say I'd recommend it. Back when I was young and invincible, I learned to draft on a motorcycle. I could tell by the buffeting and the sound of the air where the optimum spot was. For drafting, I mean, not longevity.

Drafting with two similar sized vehicles - especially bicycles - gives an advantage to both. With a big truck and a little car, not so much.

 

It does improve mpg but I think the risks are not worth it. You will get paint dings and chips from all the stones and other road garbage thrown at you by the wheels. Just last week an 18-wheeler in front of me had a blow out. A HUGE chunk of rubber went under my Pri and out the from under the left fender panel. Pulled the panel off on one side next to the door and knocked off a protective cover underneath the car. When the rubber exited it flipped up onto the left edge of the rear bumper and made and inch groove in the bumper. I could not avoid the rubber because I was in the middle lane and sandwich between two cars. The car behind me then took the rubber on the grill. Big rigs going through Texas are very loosly regulated. They are allowed to drive with bald tires and skimpy flaps that let everything fly into you. I would gladly pay 10 times the shipping costs for air or rail to get trucks off the road.