Safely follow a truck on the highway with Prius: 65 - 85 MPG

I was drafting a Suburban just yesterday.

And some people don't think there's any purpose for them. :lol:

 

I *NEVER*NEVER* 'draft' thus eliminating or substantially reducing the risk of 'rear-ending' the vehicle ahead of me. It's difficult to maintain a 'bubble of safety' with tailgating drivers, but I do my best to maintain a very minimum of 2-seconds between me and the vehicle ahead. I value my life much more than a little fuel economy.

Another consideration, 'drafting' a large truck may put you in that driver's blind spot... not a comfortable place to be should the truck encounter the necessity of a panic or emergency stop or slowdown.

 

<div class='quotetop'>QUOTE(Charles Suitt @ Mar 9 2007, 12:48 PM) [snapback]402867[/snapback]</div>

If he needs to stop he's going to stop. If somebody hits him that's their problem. Same reason I'm not going to just mow down a pedestrian because somebody's tailgating me.

That said, I don't advocate drafting. Yes, there's a definite FE gain. But too much crap can happen when you're 20 feet from the back of a truck, not the least of which is debris from the road or a blown tire on the trailer. Not worth it for legal, financial, and common sense reasons.

Following a slow-mving truck at a safe distance is a different story. Driving alone at 10mph below the speed limit imposes a certain risk of getting hit from behind or at least becoming the object of many an angry driver. A big giant trailer at the same speed ahead of you serves as a better visual for approaching drivers and encourages them to change lanes in advance rather than plow through that convenient hatch.

 

I won't go publically advocate drafting, but will comment on some of my long trips I've gained 20% or more on fuel economy and ScanGage showing a 7F increase on coolant temperature. Driving adjacent or 2-3 lengths behind a big rig will have less dramatic results, but is definately less risky.

I just don't get tempted to do it in urban traffic - not long enough, too much unpredictablity. So I just get up earlier to go to work.

In my dreams, I'd have a front bumper that would telescope three feet ahead to both serve as a crash buffer and improve the Cd drag

 

usbseawolf2000,

What you are doing is well inside my comfort zone, and it is a testament to the wake of a big rig.

For me, having a nav is good in case I miss seeing an exit sign.

 

I would clarify that I was about 3 to 4 car lengths behind the Suburban, but could see some effect on the instantaneous mpg. I don't believe in tailgating.

 

Well the "rule" as far as I know it is 1 car length for every 10 MPH- so 2-3 car lengths on the freeway is tailgating as far as I am concerned. In another career I wrote many a tailgating ticket based upon that formula, all of which were affirmed by the court. Following a tractor/trailer combination that close is just plain dangerous. Please do not do it.

 

I'd like to mention the other type of tailgating that is much more common. In large urban areas like NYC, LA, Chicago, Dallas, etc.... if there is a car length between you and whoever is in front of you, it will be taken and that's not just during rush hour. From both a fuel economy and safety standpoint, it's foolish aggression.

/end tangent

 

I decided to see how well this works out durring my commute to school which consists of a 120mile round trip 4-5days a week.

My milage avg. has been 44-45mpg with one 47mpg day because I spent so much time in stop and go traffic. The average temp during the commute has been 50deg.

I filled up the tank and proceeded to draft big rigs all the way to school and back then to my girlfriends house and wound up with 220miles on the trip and 53.2mpg avg. on the display. This is about an 8mpg difference. I started driving normal again and the avg. milage dropped to 49.4mpg with 374 miles on the trip. This gain is due in part to the slower speeds I drove while following the big truck which took me as low as 55mph and no higher than 65mph. My normal commute usually goes no higher than 65mpg unless I am passing or letting someone by.

I do not feel I was tailgating at all. I remained about 3 normal car lengths back or about 4 Prius lengths. I did not feel this was an unsafe distance with the exception of maybe a blowout. Would I advocate this type of driving? Probably not but I'm comfortable with it and the milage gain is pretty decent.

*Note* I do have aftermarket wheels and a big stereo system so my milage is not as high as some other Prius owners

 

all,

i want to thank you all for the trips on drafting from houston to orlando.

sadly it won't matter because my life is in a state of vertigo.

 

<div class='quotetop'>QUOTE(F8L @ Mar 11 2007, 07:34 PM) [snapback]403983[/snapback]</div>

I follow trucks not to draft but because they cover my preferred cruising speeds. It is especially helpful when going up hills when you can drop to 55 mph behind the truck and no one cares.

Bob Wilson

 

I also like to follow a nice truck at 55-60 mph. I make sure I'm several car length behind. No one can fault me for not going faster. See? There's a big, honkin' truck in front of me!

I just went round trip to L.A. about 200 miles with 51.7 mpg. I didn't go 55 the entire time. More like 65-70 going and 55-60 returning. Still got great mileage.

And the nice lady at the Chevron station let me fill my tires for free. I usually have to pay. Sure enough, when they aligned my tires they dropped my pressure to the recommended. I pumped it back up to 42/40. No wonder I couldn't get it over 46 mpg.

 

<div class='quotetop'>QUOTE(bwilson4web @ Mar 11 2007, 08:35 PM) [snapback]404023[/snapback]</div>

That is a secondary benifit. I never go below 65mph because I don't want to be one of those "freaks" in the slow lane messing up the flow of traffic but behind a big honkin' truck, like Godiva said, I'm safe to go slower and get better milage.

 

Just a little factoid:

When you draft another vehicle, that vehicle's gas mileage drops - as he is in effect towing you behind him.

THIEF.... B)

 

<div class='quotetop'>QUOTE(John in LB @ Mar 12 2007, 07:00 AM) [snapback]404153[/snapback]</div>

Do you have a link elaborating on this? On a less controversial use of drafting, pilots in World War II did it all the time in flying formations - they would know for sure.

 

<div class='quotetop'>QUOTE(John in LB @ Mar 12 2007, 08:00 AM) [snapback]404153[/snapback]</div>

That makes sense... if it's true, then it may not be in anyone's best interest to draft large tucks because the amount of fuel they'd consume to make up for it would be pretty disproportionate to the fuel consumption in a Prius. I guess we'll have to get someone to do an experiment. Get a big rig driver in on it, and try it w/ and w/o a Prius drafting!