http://articles.moneycentral.msn.com/SavingandDebt/SaveonaCar/Get50MpgInYourOwnCar.aspx
definition: the art of wringing every last ounce of fuel efficiency out of a car
I never knew there was actual term for this, and i've been hypermiling in my car for years. I shut off my car while waiting as Looooong red lights or CHP traffic stops on the freeway, and sometimes even fold in my side view mirror(s) when driving across the desert. The latter actually gets me 1mpg more per folded mirror!
Quote from: deweey on May 21, 2008, 01:32:58 PM
I shut off my car while waiting as Looooong red lights or CHP traffic stops on the freeway...
This probably uses more gas than idling...
Quote from: sqweak on May 21, 2008, 01:52:49 PM
This probably uses more gas than idling...
read rule number two...
To idle is to sin. Cars of recent vintage have fuel-injection systems that make starting an engine more efficient than idling. So if you're going to be at a standstill for 10 seconds or more, cut off the engine. And if the drive-through line at McDonald's is a long one, park and buy your food inside.
My question is: does the fuel savings outweigh the cost of the increased maintenance... because the starter in a standard gas vehicle is not designed to cycle that many times for a given number of miles traversed, so you're gonna be replacing it more often. You're also hitting the starter gear teeth into the flywheel ring gear teeth more often than it was designed for, which *could* lead to earlier flywheel replacement (as many modern cars do not have a separately replaceable flywheel ring gear like the old stuff did).
I've been tempted to shut off my VR6 when I approach lights I know to be long (I already do if I come up on a railroad crossing where I have reason to believe I'll be waiting at least 1 minute)... but I really don't want to replace the starter in that car anytime soon.
I do wonder what kind of gas mileage a 2.8l VR6 would get if one "hypermiled".
Pretty cool! [thumbsup]
Someone try this on a bike and see what happens ;D
My car averages around 10 mpg in the city. I got 27 on the highway at steady speed with the cruise control on for an entire tank on a long trip, and I was thrilled.
Don't think the techniques will help much in my gas sucker. I drive a fuel pig and I accept that, and I get irritated by people who think they can magically increase their MPG rather than buying something more efficient. I hear that kind of BS all the time on the Infiniti / Nissan forums. Product X got me an extra 2 mpg! Product X is a placebo, you just happened to get 2mpg more because you were light on the pedal, or from regular variance in driving conditions. You name it, it's been covered. Acetone, fuel types, magnets on the fuel line, intake gimmicks...
I don't agree with the "max tire pressure" suggestion. High tire pressure increases wear on the treads amd reduces grip A LOT (meaning you'll have longer stops in emergency braking and poor grip under hard cornering). That's assuming the tire is good enough to handle the pressure without blowing out (old tires with hard rubber and cracked sidewalls would be dangerous to overinflate). Maybe 5 psi over is the factory number is "acceptable" but if you go balls out and put the maximum load you are asking for trouble.
i found out about this the other day...and i've been reading up on it. seems like there is a whole sub-car-culture based around it. pretty cool
a couple websites:
www.hypermiling.com
www.cleanmpg.com (they have some good descriptions of stuff)
a good list of hypermiling tips
http://tinyurl.com/6r5vf4
From the tinyurl posted above
Drafting: This technique comes with a warning sign: according to many hypermiling experts, it is incredibly dangerous. A “deliberate form of tailgating,†the forced auto stop involves turning off your car's engine and then following closely behind the vehicle in front of you “in order to take advantage of the reduced wind resistance in [the other car's] immediate wake.â€
Im all for better mileage, but I can't think of a more stupid thing to do while driving a car. Shutting it off while drafting someone? Vacuum assisted brakes and power steering would be off the table if an emergency stop/evasion situation popped up.
[roll]
I think I'm an anti-hypermiller. It's not that I floor it everywhere I go... I just don't care. Incidentally, the first time I took my wife's new Pious for a drive a increased her average fuel consumption somehow. I really have no idea how- but she tries (still n00b) to do this hypermillifying type behavior when she drives. /shrug
Quote from: c_rex on May 21, 2008, 05:18:18 PM
I think I'm an anti-hypermiller. It's not that I floor it everywhere I go... I just don't care. Incidentally, the first time I took my wife's new Pious for a drive a increased her average fuel consumption somehow. I really have no idea how- but she tries (still n00b) to do this hypermillifying type behavior when she drives. /shrug
Since I received my driver's license, I've gassed it hard, braked hard. I loved hearing my engine rev hard while pushing it through some twisty backroads. I'd go 25 miles out of my way on the commute home so I could drive some desolate backroads that had great curves.
But honestly...The way gas is going up, and the rest of the economy going down....I've got to start trying to save a little money on fuel. I don't know about all their hypermiling techniques, but there are a few tid-bits that I might adapt...I dunno :-\
I watched a hypermiler driving on TV. Driving well under the speed limit and coasting while paying more attention to a computer does not seem like a good idea to me.
I took home a Camry Hybrid today...so I can drop it off tomorrow for a promo.
I caught myself trying to keep it on 'electric' only a number of times. :-\
I still averaged 49.8 for the 18 mile drive (50/50 highway/city).
Jeremy Clarkson from Top Gear "Hypermilling" a Audi A8
http://video.google.com/videoplay?docid=-4113162060604318409&q=top+gear+audi+a8&ei=8P80SJDDOJHCqAOEz5SuCQ&hl=en
Quote from: Randimus Maximus on May 21, 2008, 10:04:57 PM
I took home a Camry Hybrid today...so I can drop it off tomorrow for a promo.
I caught myself trying to keep it on 'electric' only a number of times. :-\
I still averaged 49.8 for the 18 mile drive (50/50 highway/city).
Reminds me of something i saw on the local news. Some company installs an "electric motor only" button on the prius for driving around town that significantly increases your mpg... but they charge some absurd amount(in the thousands) for it.
HEY WHERES THE REST OF THAT VIDDEO???
Quote from: He Man on May 21, 2008, 11:18:50 PM
HEY WHERES THE REST OF THAT VIDDEO???
Looks like it was removed >:(
It was on youtube, after a Internet search, I found other sites that used to host it, but they removed it as well. Probably threaten with copyright or something.
Do you want the spoiler?
he makes it all the way back
Quote from: He Man on May 21, 2008, 11:18:50 PM
HEY WHERES THE REST OF THAT VIDDEO???
Yes, that's pretty frustrating. Useless, in fact.
I baby my '97 Taurus with 173,000 miles. I don't do the mirrors thing & shut the motor off though. I ease off the line at lights/stop signs, plan my routes to avoid the handful of heavy traffic & long lights in town (I can do this without making more than a mile difference on my drive) and never go through drive throughs at the bank/fast food. I also don't stomp down the pedal to regain speed after slowing in a curve or speeding up for an on-ramp. In a well-worn, heavy, underpowered car, I'm managing 25-27mpg and have seen as high as 29 in mixed driving.
JM
I filled up this morning and have been going out of my way to drive "nice." Normally, my mpg meter would say 18-19, and Im at 21 right now with a peak earlier today of 23. While this is an improvement, the rest of the drivers around me are going insane with rage at my crappy acceleration.
From now on Ill probably still try to drive "nice" but Ill strike a balance between that and [evil] driving
+1 that's really the way to go - balance in all things.
I started driving a bit like that when I borrowed my mom's PT Cruiser, but for some reason it gets atrocious gas mileage for a four-banger, so it didn't do much good.
Clarkson is right in the video, it does take a lot of active brainpower to stay driving on that level since you have to anticipate things so far in advance if you plan to shun the brake much. It's a little fatiguing actually, and maddening when you hit a string of red lights.
Quote from: Monsterlover on May 23, 2008, 04:04:26 PM
While this is an improvement, the rest of the drivers around me are going insane with rage at my crappy acceleration.
lmao- so that was you!
Oh you know it was [laugh]
I do drive a lot like Clarkson was driving in that video. I shut the car off at LONG lights, and coast downhill in neutral in residential areas. I also try to avoid braking, pushing the gass pedal down more than an inch or so, or changing speed by more than 5 mph on the highway, and I get about 10% to 20% better fuel economy than the EPA estimates on my Accord.
I don't make a practice of drafting, though I will get a little close rather than slam on the brakes as long as there's not heavy traffic. I remember when Honda first introduced the Insight hybrid though that they had a contest for the car magazines to see who could get the best mileage. Car and Driver won by taking a Suburban, opening the rear door and using 2 way radio to drive the Insight wihtin 6 inches of the rear of the Suburban the whole trip. I think they managed 80+ MPG's in the Insight.
Quote from: factorPlayer on May 23, 2008, 08:20:43 PM
(snip)
I started driving a bit like that when I borrowed my mom's PT Cruiser, but for some reason it gets atrocious gas mileage for a four-banger, so it didn't do much good.
(snip)
PT's get horrible gas mileage because they are ridiculously heavy. Chrysler's stand on this fact is they wanted you to be safer in a more robust cage, therefore heavier vehicle (and horrendous gas mileage).
Maybe what Stucky said is true. My fiancée's 2004 Malibu Classis with a 2.3L 4 cyl with about 85,000 miles gets about 21-220mpg. My '97 Taurus with 173,000 miles gets 24-27mpg. I'm sure a lot of it is driving style ~
JM
so.....
coming back from the S/O's parents this weekend, I had a south wind pushing me....did about 250 miles of freeway and got 36mpg [thumbsup]
going down the wind was pushing into us and we got about 28.6
Quote from: Le Pirate on May 27, 2008, 07:49:06 PM
so.....
coming back from the S/O's parents this weekend, I had a south wind pushing me....did about 250 miles of freeway and got 36mpg [thumbsup]
going down the wind was pushing into us and we got about 28.6
what were you driving?
Quote from: BibleBoy on May 21, 2008, 02:08:38 PM
My question is: does the fuel savings outweigh the cost of the increased maintenance... because the starter in a standard gas vehicle is not designed to cycle that many times for a given number of miles traversed, so you're gonna be replacing it more often. You're also hitting the starter gear teeth into the flywheel ring gear teeth more often than it was designed for, which *could* lead to earlier flywheel replacement (as many modern cars do not have a separately replaceable flywheel ring gear like the old stuff did).
I've been tempted to shut off my VR6 when I approach lights I know to be long (I already do if I come up on a railroad crossing where I have reason to believe I'll be waiting at least 1 minute)... but I really don't want to replace the starter in that car anytime soon.
I do wonder what kind of gas mileage a 2.8l VR6 would get if one "hypermiled".
I doubt that you'd see much difference in the wear of a starter if you shut it off at lights and such. You'd probably still be ahead $$$ wise in the fuel savings.
I remember watching something on Discovery years ago where engineers were attempting to break a mileage record on a closed course - the did so by accelerating to top speed WOT, then drifting to almost a stop, repeat. I can't be troubled to find factual info, but here (http://www.greenhybrid.com/discuss/f13/accelerate-fast-best-mpg-15047/) is the gist of it.
I call bull on waiting to accelerate (http://www.hypermiling.com/acceleration-costs-fuel.html) with an auto - this magical forward momentum comes from someplace.
Quote from: il d00d on June 03, 2008, 08:05:06 PM
I call bull on waiting to accelerate (http://www.hypermiling.com/acceleration-costs-fuel.html) with an auto - this magical forward momentum comes from someplace.
Yeah...your torque converter. You use the same energy at idle no matter what, however with no fuel applied, an automatic car will move forward. That's why you need to keep your foot on the brake. They are correct-they're suggesting you allow the car to start moving while at idle, thus making sure that as you accelerate, you do not have to break static friction.
Though if they really cared they'd get a moto [moto]
Quote from: someguy on June 03, 2008, 08:19:17 PM
Though if they really cared they'd get a moto bicycle (http://www.freesmileys.org/smileys/transport028.gif)
fixed ;)
Hyper-milers are using up my life. There is no commodity on Earth that I value as much as my time. It is the ultimate non-replenishable resource. If you don't value yours fine, stay in the right lane. >:( For me that's 30min a day I coulda spent with my daughter, I could care less if I gotta burn an extra $10 weekly in dinosaur remains.
Quote from: WannaDucBad on June 03, 2008, 08:44:58 PM
Hyper-milers are using up my life. There is no commodity on Earth that I value as much as my time. It is the ultimate non-replenishable resource. If you don't value yours fine, stay in the right lane. >:( For me that's 30min a day I coulda spent with my daughter, I could care less if I gotta burn an extra $10 weekly in dinosaur remains.
On the other hand, I've found that not being in as much of a hurry as I thought I was in is quite pleasant. It can be stressful trying to maintain a high speed on the interstate (mostly because people in California don't know how to drive, but in general as well), whereas maintaining a reasonable speed and staying out of the way of the bulging-forehead-vein-brigade makes things a lot easier. It really doesn't take that much longer, either.
Quote from: WannaDucBad on June 03, 2008, 08:44:58 PM
Hyper-milers are using up my life. There is no commodity on Earth that I value as much as my time. It is the ultimate non-replenishable resource. If you don't value yours fine, stay in the right lane. >:( For me that's 30min a day I coulda spent with my daughter, I could care less if I gotta burn an extra $10 weekly in dinosaur remains.
Hurry home so you can waste time on the DMF?
Really?
Quote from: WannaDucBad on June 03, 2008, 08:44:58 PM
Hyper-milers are using up my life. There is no commodity on Earth that I value as much as my time. It is the ultimate non-replenishable resource. If you don't value yours fine, stay in the right lane. >:( For me that's 30min a day I coulda spent with my daughter, I could care less if I gotta burn an extra $10 weekly in dinosaur remains.
DMF = daughter ??? ;D
It's a matter of choice. I don't commute for fun, I'm not there for a joy ride. Daughter's young, she still sleeps quite a bit. She helped Daddy work on the bike earlier. Look the point is if you wanna go the speed of slow that's fine, like so many other things here in the US it's about personal liberity. Don't infringe on my choices though, get out of the way, stay in the slow lane, and don't give me dirty looks when I squeeze between you and grandma in the old Ford. Because you two are having slow drags, you bet your granola ass I'm gonna squeeze through there the very second I can do so without leaving paint. And yeah I'm gonna do it with the petal mashed, the 4 barrel howling, and the dual exhaust roaring. Before you accuse me of be the rude one, remember I wouldn't have acted that way if you weren't being inconsiderate of others on the road first. There's a reason that Interstates have minimum speed limits posted. It's a hazard to other drivers when a car is going well below the flow of traffic speed. Another bug of mine is when I finally get around one of these Hyper-milers, only to get caught at the next light and they pull up looking all smug, you know what? I've timed these lights, given a certain speed of acceleration from any given light and a certain flow of traffic. I can get almost to work with very few lights. Don't sit there like "see we're at the same light anyway Mr. Speedy", because I wouldn't have been if you hadn't been in my way! >:( When I'm driving I try to think about others, "if I turn right in front of oncoming traffic, can I get out of the way before they get here or will they have to hit the brakes, because I'm to slow". If I can't get out of the way I wait until the traffic is past. If I'm cruising along and someone comes up going faster than me, I get over. It's not hard people, try to keep the flow of traffic as smooth as possible and we'll all save money and time!!!
Quote from: someguy on June 03, 2008, 08:19:17 PM
Yeah...your torque converter. You use the same energy at idle no matter what, however with no fuel applied, an automatic car will move forward. That's why you need to keep your foot on the brake. They are correct-they're suggesting you allow the car to start moving while at idle, thus making sure that as you accelerate, you do not have to break static friction.
Though if they really cared they'd get a moto [moto]
Oh yeah, I get what they are saying - the amount of energy required to go from a dead stop to rolling is probably best illustrated by an 18 wheeler under load - they luuurch and twist forward. With an auto, you don't want to power-break from a stop, but at the same time, they seem to suggest that this is "free" energy, which it isn't. It is probably the same amount of energy you would apply to the wheels on a car with a manual transmission to go from a dead stop. You might even argue that brakes applied against the idle "momentum" is a huge waste of energy over time, since that power is transferred to driveshaft, etc. Now, I don't know the finer points of the mechanics of a slush box, but I would think that being in neutral would be preferable to having the brake applied if you are at a dead stop for a period of time. If nothing else, you are saving the energy losses associated with transferring power from engine to wheels. But the moral of the story here is to use any momentum to your advantage.
Quote from: il d00d on June 03, 2008, 09:59:28 PM
With an auto, you don't want to power-break from a stop, but at the same time, they seem to suggest that this is "free" energy, which it isn't. It is probably the same amount of energy you would apply to the wheels on a car with a manual transmission to go from a dead stop.
It's not free but it's kinetic energy that is not being used. It is NOT the same amount of energy you would use from a dead stop. Static friction is fairly sticky. Ever push a car? Hard to get it going, easy to keep it going. It's the same idea-letting the car start rolling, then you start pushing.
Quote from: il d00d on June 03, 2008, 09:59:28 PMYou might even argue that brakes applied against the idle "momentum" is a huge waste of energy over time, since that power is transferred to driveshaft, etc. Now, I don't know the finer points of the mechanics of a slush box, but I would think that being in neutral would be preferable to having the brake applied if you are at a dead stop for a period of time. If nothing else, you are saving the energy losses associated with transferring power from engine to wheels. But the moral of the story here is to use any momentum to your advantage.
Most automatics idle lower in gear than in neutral (at least, the older ones do). Putting it in neutral would burn more gas than sitting with the brake on.
Annnnd if you really want to save gas and not get shot at....just accelerate slow, leave plenty of room so one doesn't have to brake as often (and therefore reaccelerate), check the tires, tune up the motor, drive a good speed in the proper lane and get a life.
Speeding there really doesn't save you that much time. 60 Vs 80 saves you twenty minutes.....if you're going 60 miles. It saves you ten if it's thirty miles. 15...which is maybe average...a whopping 5 minutes. Catch a light, forget your keys, *anything* goes amiss, and the only thing you managed to do is abuse the car and risk a ticket. Just leave the dang house earlier-you're time isn't that valuable.
I don't speed to work....and if our product is late...it's a $4,000 charge.....
....per hour.....
OY! I want to see the end of that video. Not just to see the outcome (thanks for the spoiler), but to see the techniques and hear the chit-chat on the subject. Those shows carry alot of info in the banter...
I drove my old jeep up to see my gf for lunch today. About 70 miles each way. Instead of rolling down the windows (source of drag), I just took the doors off. And to account for the drag of having no doors, I removed the back window as well. ;D Not efficient, by any means, but awfully nice way to spend a long drive. 8) Sorry sad gas-guzzler that it is, it only used half a tank. But with a top speed of 55, I spent all the gas money I would have saved on coffee to keep my brain occupied. ;D
[/random threadjack]
Okay, i'll clarify my idea of "hypermilling"
1. I dont drive at granny speeds in the highway, let alone in the fast lane. I once calculated 5 more MPG by going 60mph(in the slow lane mind you) but its just not worth the time/cost benefit to me... 70mph is acceptable.
2. I do leave the car in Neutral gear with parking brake applied whenever i'm at a stop. If that stop is going to be for an extended amount of time (i.e., a minute) then i'll shut off the engine.
3. I try really hard not to brake on the freeway, and it annoys the hell out of me when the aforementioned granny keeps hitting the brakes for no apparent reason. Sometimes my foot off the brake will cause me to slightly tailgate... my apologies.
4. If I see a green light ahead when I exit the freeway(with long offramps) then I'll shift the car into neutral and prepare to coast to a stop because I know i'm not gonna make that green.
5. If i see that said light just turning green as I'm exiting, i'll keep my speed up cause worse case i'll make the yellow. This also holds true for some of the lights around my neighborhood.
If you're caught behind me while i'm coasting, then deal with it.. i'm not gonna keep my foot on the gas only to start braking when that light turns yellow and we're still 50 yards away.
My point, Hypermilling doesn't necessarily mean you're holding up traffic. Sure, like all things, some people take it to the extremes... but I enjoy my 27mpg on my 2.7L V6 and I hardly drive slow.
Quote from: someguy on June 03, 2008, 10:20:35 PMjust accelerate slow, leave plenty of room so one doesn't have to brake as often (and therefore reaccelerate)
As an added benefit, avoiding such stop-and-go driving actually smooths out traffic. When you're not driving that way, the people behind you don't have to either.
Quote from: someguy on June 03, 2008, 10:20:35 PM[...]and get a life.
[laugh] Always good advice.
Quote from: someguy on June 03, 2008, 10:20:35 PMSpeeding there really doesn't save you that much time. 60 Vs 80 saves you twenty minutes.....if you're going 60 miles.
Even that is assuming you can maintain 80 the whole way. You'll invariably run into something that will slow you down. At 65, this is less likely, or at least less likely to slow you down by
as much.
Just by not driving like a bat out of hell, I end up getting 22MPG out of a truck rated for 17. Still sucks, and I'm not paying for the gas, but it's nice to not be wasteful for no reason.
Quote from: someguy on June 03, 2008, 10:14:03 PM
It's not free but it's kinetic energy that is not being used. It is NOT the same amount of energy you would use from a dead stop. Static friction is fairly sticky. Ever push a car? Hard to get it going, easy to keep it going. It's the same idea-letting the car start rolling, then you start pushing.
Most automatics idle lower in gear than in neutral (at least, the older ones do). Putting it in neutral would burn more gas than sitting with the brake on.
Well, if it gets you moving, it is the energy that you would use from a dead stop. I think that static friction is technically the force that would defeat the static condition of tire against ground (resulting in in tire spinning against ground - which for the record, I am 100% in favor of)
As for idle, we're talking relative engine speed, which is not the same as relative energy wasted. Imagine bench pressing a broom handle Vs maintaining the up position in a push up. Wasting energy on pumping losses (going through the motions in idle) vs defeating the force of motion.
Quote from: il d00d on June 03, 2008, 10:49:35 PM
I think that static friction is technically the force that would defeat the static condition of tire against ground (resulting in in tire spinning against ground - which for the record, I am 100% in favor of)
I'm not sure where you're getting your information from.
Static friction:
fmax = μs n
The force of static friction increases up to a maximum value, after which the object "breaks loose" and begins to start moving.
Kinetic friction:
f = μkn
(http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/Dynamics/gifs/Forces12.gif)
Keeping moving...through whatever method....is the ideal here.
As for your last sentence "As for idle, we're talking relative engine speed, which is not the same as relative energy wasted. Imagine bench pressing a broom handle Vs maintaining the up position in a push up. Wasting energy on pumping losses (going through the motions in idle) vs defeating the force of motion."
I can't address that, as I have no idea what you're saying...
"relative engine speed"? "relative energy wasted"?
Relative to what?
Thanks for the drawing :P
Gut check: when you say breaking static friction, are you talking about the relationship between the tires and the ground or something else? When starting from a stop, do the tires ever break loose ?
Quote from: someguy on June 05, 2008, 12:43:20 AM
Relative to what?
Each other. I was about five beers deep at the time, so let me rephrase. Because the engine is moving slower (automatic, in gear, at rest because brakes are applied) does not mean it is using less energy than an engine moving faster in neutral. When the car is in gear, the engine is under load whether it is producing forward motion or not - the engine is producing enough power to start from a stop, but may be stopped by the brakes. When a car is in neutral, the engine is making enough power to move itself.
I think the point you are trying to make is the automatic leverages the energy wasted by being in neutral, idling. But the car is not idling. It is in gear, continually producing enough power to get the car rolling. Also, all things being equal, the energy required to produce forward motion is the same whether the car is equipped with a manual or automatic transmission.
Now, my argument is predicated on the assumption that when the car is in idle the engine uses/gets less juice - I have absolutely no way of proving that (easily anyways), but it makes sense that it would. And, well, for the record, I did say "one could argue", which is what I am doing here. Anyways, good chatting with you..
I tried the accelerate slow thing and did get better mileage, but only by 2mpg.
What really works is drafting semi's on the highway. I get between 1 and 3 car lengths and shift into neutral on flat ground or going down hill. They sort of "pull" you along. Going down a slight grade seems like I can coast for 30 seconds or so (at 65-80mph)
My xl7 is rated 24 hwy and ive had it up to almost 30 in mixed driving ;)
Drafting semi's is a lot of work though, mentally. It's not a habit I plan to maintain, mostly I was curious how much it would help.
Quote from: Monsterlover on June 05, 2008, 10:05:38 PM
I tried the accelerate slow thing and did get better mileage, but only by 2mpg.
What really works is drafting semi's on the highway. I get between 1 and 3 car lengths and shift into neutral on flat ground or going down hill. They sort of "pull" you along. Going down a slight grade seems like I can coast for 30 seconds or so (at 65-80mph)
My xl7 is rated 24 hwy and ive had it up to almost 30 in mixed driving ;)
Drafting semi's is a lot of work though, mentally. It's not a habit I plan to maintain, mostly I was curious how much it would help.
+1
i was driving a friends rental this past weekend and it had one of those instant mpg readouts. I tried driving behind a semi to see how close i'd have to get in order to see any real result. Suprisingly, I got 20 more mpg at even 2 car lengths behind the truck! Didnt try driving any closer for safety reasons, but i'd imagine if you were up on the semi's ass you'd get spectacular range.