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I've noticed a increase in my mileage when I draft (tailgate). What is your input on the subject.... I get an increase of about 15%. In fact my best mileage was behind a semi hauling caskets, I averaged 69 MPG for the whole tank.
 

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At highway speeds the most significant contributor to fuel consumption is air resistance. So drafting has a huge impact on mileage.
But obviously the safety risk to fuel benefit factor has to balanced to determine your drafting distance.
 

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the good and bad

The good - much better fuel efficiency

The bad - FAR more rock chips on paint and windshield. Also, increased dangers in terms of less visibility

Is that worth saving a few bucks in gas? your call...
 

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rangeman said:
I've noticed a increase in my mileage when I draft (tailgate). What is your input on the subject.... I get an increase of about 15%. In fact my best mileage was behind a semi hauling caskets, I averaged 69 MPG for the whole tank.
CVT or 5MT?

I agree with leeper on the downsides and would add:
(1) greater increase in mpg the closer you are, so it gets REALLY dangerous
(2) staring at the back of a truck quickly gets boring
(3) most trucks are moving way too fast for good mpg anyway

That said you often pick up a little suction from the sides of passing trucks or further back as they pull away, and they help to bust up headwinds.

IME the way to better mpg is lower speeds and pulse and glide (engine-on unless you are comfortable turning it off). I have an MT and today for example did 120miles in two segments (two warmups from cold) and averaged 97.9mpg overall running around 50-55mph except for the first and last 6 miles, which is 35-40mph. And I wasn't drafting close behind anything. This is fairly typical for a summer no-wind day (tailwind improves things obviously; rain or headwinds hurt).

I don't think I would do better than that drafting right behind a semi, which would probably be running at 65mph-ish, unless I stayed within <10 feet of him, which would be outrageously dangerous and boring, not to mention damaging to the front of my cherished Insight. So I don't draft semis.

P.S. Yes I have the MIMA but use it so far only to shove a little extra regen into the battery when needed.
 

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the mythbusters(one of my favorite shows, watching it right now actually :lol: ) proved that drafting does work and the closer you draft the better the effect

of course, to get the best effect you would need to be drafting approx. 4 ft behind the semi..and thats just crazy

plus, as stated already, semi's usually drive too fast for optimum mpg anyway(here usually 70-75)

although if i am running a little late and do HAVE to drive at those speeds, i will usually latch onto the back of a semi and maintain a slight draft to try to minimize my "o sh*t im late" driving :lol:
 

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We have already scapped too many irreplaceable Insights due to other bad drivers and crazy deer to risk of becoming an ornament on the back of the truck. In addition there is the the effect of stress on our body and the health hazzard of breathing in carcinogenic Diesel exhaust. Plus it really peeves the truck driver when he can't see you and it implies to other motorists that our Insights are so underpowered that we need to draft a truck to maintain highway speeds.

If you must draft something though, make it a Hummer. ;)
 

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No doubt drafting substantially reduces fuel consumption.

Back in Jan of 2000, someone from Car and Driver drafted inches behind a Ford Explorer with a plywood back to simulate an 18-wheeler. They had cell phones and it is not relaxing driving. I've gotten about 75mpg cruising at 58mph, but with this extreme drafting he got 121mpg over 100 miles - about a 50% increase.

I've done it in the past and noted ScanGage registered the coolant temperature rose from 195F to 207F.

I discourage close drafting like this for a number of reasons. Unless you know the route by heart or have a NAV unit, you will pass the exit by the time you see it. In an urban area, you won't get to draft for an extended time and traffic is crazy as it is.

If you have read readers comments to the hypermiling articles published this year, flamers love to give a very distorted pictures of hypermilers - kind of like all bikers are hoodlums in gangs. :roll: Their favorite distortions is poking in the left lane and close drafting. Most hypermilers I know seldom if ever do those things. Close drafting is toxic PR so I avoid it.
 

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Delta Flyer said:
to give a very distorted pictures of hypermilers - kind of like all bikers are hoodlums in gangs. :roll:
i know what thats like, i ride too

im always doing everything i can to NOT give hybrids a bad name
 

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"We have already scapped too many irreplaceable Insights due to other bad drivers and crazy deer to risk of becoming an ornament on the back of the truck."

I have to wonder about this. If you're drafting 4 feet away, sure, but in my case I'm generally no closer to the rear of a truck than the truck is to the car in front, and I dare say I could stop quicker than 40 tons of loaded semi.

"In addition there is... the health hazzard of breathing in carcinogenic Diesel exhaust."

Which you get no more of (maybe less) drafting close behind a truck than out in the general flow of traffic. Look at where the truck's exhausts generally are, and the airflow pattern behind it.
 

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james said:
in my case I'm generally no closer to the rear of a truck than the truck is to the car in front, and I dare say I could stop quicker than 40 tons of loaded semi.
Keep in mind (a) trucks are often one car length behind the car in front of them at 65-70mph (very dangerous on their part, but at least they can see over the car and anticipate, which you can't), (b) no doubt you'd stop faster than the semi if the brakes are applied full on at the same instant, but you need to add in your reaction time plus the time it takes you to realize that the truck is braking hard rather than just easing on the brakes, and (c) the draft decreases rapidly the further back you are (look at the closeness of NASCAR drafting, and they are at 150-200mph where the draft pockets are longer).

james said:
Which you get no more of (maybe less) drafting close behind a truck than out in the general flow of traffic. Look at where the truck's exhausts generally are, and the airflow pattern behind it.
I wouldn't count on it. The exhaust stacks feed into the airflow over the top of the trailer which is then sucked down by the vacuum just behind the rear of the trailer.

But it's your call. As I said I find I actually get better mpg by driving lower speeds and not drafting, and it's more relaxing.
 

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Well, I know my reaction & braking times, and drive accordingly. And I have watched the diesel exhaust from a typical truck, when there's a bit of smoke, and it goes over a box trailer and mixes well behind.

As for speed, on the route I drive where I might consider drafting, the trucks are generally going 55-60ish, while the general flow of traffic is 65 and up. A lot of my "drafting" is really me sitting behind a slow truck waiting for an opening in the lane to the left :)
 

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Discussion Starter #12
heres how i do it i find the right semi going as fast as i want to go. you do have to adapt to their speed. you must be able to read their plates when in the zone. let them know you are there. help them shift lanes.
 

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james said:
I think that car carriers work the best, or moving vans. Anything that's low to the ground.

i would definitely NOT recommend following a car carrier.. I was driving home one day behind a car carrier, and all of a sudden i saw this huge black what looked like piece of plastic or something.. coming straight at me.. so i swerved out of the lane (luckily nobody was next to me) and apparently the sun roof of one of the cars just flew off.. it looked like it weighed nothing at 70 mph :) but I'd still be careful.
 

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... my best mileage was behind a semi hauling caskets, ...
His cargo should have told you something, how really dumb that drafting nonsense is.

Fred / Proud Owner of "The Silver Bullet"
 

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I do a lot of highway driving on my commute and always look for an opportunity to draft, but I try to keep a safe distance. A slight draft is better than no draft IMO. It usually gets me another 10mpg on my 120 commute.
 

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Lenictavus said:
i would definitely NOT recommend following a car carrier.. I was driving home one day behind a car carrier, and all of a sudden i saw this huge black what looked like piece of plastic or something.. coming straight at me.. so i swerved out of the lane (luckily nobody was next to me) and apparently the sun roof of one of the cars just flew off.. it looked like it weighed nothing at 70 mph :) but I'd still be careful.
Tire treads too. I was on a trip today, and the tires on many of the semis that went by were making "I'm-about-to-separate" sounds. Scary!!

As I said before I'm pulling 90-100mpg from my MT Insight without drafting, and there are people who are doing even better, and they don't draft either. So it seems a pointless risk to me.
 
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