2 Second gap = 32mpg
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NGL450 w/EORP, S550
2 Second gap = 32mpg
Found a couple of interesting things this weekend while putting almost 1000 miles on the GL in four different trips covering most of the Cali-Nevada area:
1. The roof rack cross bars take away 2mpg. I removed them and sure enough, we now average 25 mpg vice 23. Wind noise is reduced by a factor of ten. It's super quiet and like driving a vault. With the cross bars I could hear the wind over the sunroof.
2. A two second gap between between you and the car ahead of you who is also 2 seconds behind a truck equals 32 mpg at 60 mph. DISCLAIMER: Do not tailgate in order to save fuel. I found that I don't need to if the car ahead is at the right distance from the truck and I maintain the correct gap between me and him. If you've ever tailgated a truck in order to watch your mpg skyrocket, don't. It's dangerous. Let someone in front of you, then ease off to maintain a 2 second gap behind them. Hope that they maintain a 2 second gap to the truck, and here's where it can fall apart. The fellow in front of me was cooperating; however, and for 30 miles my mpg rose steadily from 25 to 32 mpg.
The aerodynamics involved basically boil down to that the car ahead's bow wave is deflecting the vortex generated by the truck up and over you. I don't know what that guy's mileage was, but I imagine that he paid by a couple of mpg by pushing that truck vortex up and away from me. Before the peanut gallery chimes in on how dangerous this is, a 2 second gap in the driving conditions we were experiencing were sufficient in order to safely stop.
If you're tired, at night, in rain, sleet or snow - no way no how.
1. The roof rack cross bars take away 2mpg. I removed them and sure enough, we now average 25 mpg vice 23. Wind noise is reduced by a factor of ten. It's super quiet and like driving a vault. With the cross bars I could hear the wind over the sunroof.
2. A two second gap between between you and the car ahead of you who is also 2 seconds behind a truck equals 32 mpg at 60 mph. DISCLAIMER: Do not tailgate in order to save fuel. I found that I don't need to if the car ahead is at the right distance from the truck and I maintain the correct gap between me and him. If you've ever tailgated a truck in order to watch your mpg skyrocket, don't. It's dangerous. Let someone in front of you, then ease off to maintain a 2 second gap behind them. Hope that they maintain a 2 second gap to the truck, and here's where it can fall apart. The fellow in front of me was cooperating; however, and for 30 miles my mpg rose steadily from 25 to 32 mpg.
The aerodynamics involved basically boil down to that the car ahead's bow wave is deflecting the vortex generated by the truck up and over you. I don't know what that guy's mileage was, but I imagine that he paid by a couple of mpg by pushing that truck vortex up and away from me. Before the peanut gallery chimes in on how dangerous this is, a 2 second gap in the driving conditions we were experiencing were sufficient in order to safely stop.
If you're tired, at night, in rain, sleet or snow - no way no how.
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From: NW corner of CONUS
2008 GL 320 CDI, 2004 VW V10 Touareg TDI
Very interesting observation. I've also observed a sharp increase in mileage (it didn't last more than 15 minutes so I can't quantify it) when I've had the opportunity to drive the center lane of a 3 lane freeway BESIDE a long row of trucks at nearly the same speed - traffic permitting. My theory is that the trucks get a column of air moving horizontally and at least part of that air is moving with me.
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From: Louisville, KY
2014 Black SLK 55 AMG, Black 2015 GL 550, 2011 Blue GLK 350
Mythbusters did a show on just this topic. It was drastic how much fuel economy rose tailgating a semi. Obviously as you said, very dangerous and should not be done in real life. But very interesting. Thanks for the info.
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NGL450 w/EORP, S550
No. Which is why I'm remarking that noticeable gains can still be achieved by maintaining a safe gap between you and another car tailgating the truck, without endangering yourself, your co-traficants and your paintjob.
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From: Sunny So-Cal
2011 QX56 (formerly '11 GL350)
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MBWorld Fanatic!
Joined: Jan 2010
Posts: 3,118
Likes: 782
NGL450 w/EORP, S550
Pics or it didn't happen...
http://www.youtube.com/watch?v=PVbWvEF4yNM
This went on for 50 miles maintaining the same distance. MPG ended up at 32.
PS, Tam -
I've removed the audio for privacy reasons, but you gotta believe that this car is super quiet when all is put together as it should be. Hope you get your windshield/turbo issues sorted out sharpish.
http://www.youtube.com/watch?v=PVbWvEF4yNM
This went on for 50 miles maintaining the same distance. MPG ended up at 32.
PS, Tam -
I've removed the audio for privacy reasons, but you gotta believe that this car is super quiet when all is put together as it should be. Hope you get your windshield/turbo issues sorted out sharpish.
Last edited by Max Blast; Nov 20, 2010 at 12:42 AM.
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Joined: Oct 2010
Posts: 302
Likes: 1
From: Sunny So-Cal
2011 QX56 (formerly '11 GL350)
Pics or it didn't happen...
http://www.youtube.com/watch?v=PVbWvEF4yNM
This went on for 50 miles maintaining the same distance. MPG ended up at 32.
PS, Tam -
I've removed the audio for privacy reasons, but you gotta believe that this car is super quiet when all is put together as it should be. Hope you get your windshield/turbo issues sorted out sharpish.
http://www.youtube.com/watch?v=PVbWvEF4yNM
This went on for 50 miles maintaining the same distance. MPG ended up at 32.
PS, Tam -
I've removed the audio for privacy reasons, but you gotta believe that this car is super quiet when all is put together as it should be. Hope you get your windshield/turbo issues sorted out sharpish.
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