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Old 06-12-2014, 10:45 PM   #1 (permalink)
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55mph not drafting vs 65mph drafting

which one is better?

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Old 06-12-2014, 11:18 PM   #2 (permalink)
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There are to many variables to even begin to try to answer this question.
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Old 06-12-2014, 11:33 PM   #3 (permalink)
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LOL. I clicked this link to find out the answer. It never occurred to me that someone would ask the question because it would be more difficult to calculate the answer than to observe the results of a trial run.
Gas and Electric Vehicle Cost of Ownership Calculator

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Old 06-12-2014, 11:37 PM   #4 (permalink)
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There's d . r . a . f . t . i . n . g, and there's drafting... and then there's drftn. And it will depend on whether you're behind something like this...


or this...


Complicated question.
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Old 06-12-2014, 11:59 PM   #5 (permalink)
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Originally Posted by counterbond View Post
which one is better?

Real world (and yes I have tried many times) plain and simple DRAFTING only works at 55mph, above that speed I find that the big rig varies too much in speed and the wind whips the car around too much for fuel economy to improve much. On a windy day it is better than just driving 65mph but its never better than 55mph.

Now magically drafting at 55mph makes a major difference and the amount of wind whipping the car about is almost non-existant.

The only circumstance where I have found this to be different is when the big rig has a LOW DECK trailer that almost touches the ground, then at higher speeds the car actually can track the big rig, not whip around the road and get better fuel economy, but you almost never encounter one of those on the highway.

So short answer (from years of empiracle) is 55mph is always better drafting or not than faster. Drafting affects taller vehicles like a suburban more effectively than a lower car which might actually loose FE if it whips back and forth too much. And big rigs that are taller and closer to the ground work much more affectively for drafting than a normal big rig which sometimes doesn't even help my low cars.

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Old 06-13-2014, 09:41 AM   #6 (permalink)
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Originally Posted by counterbond View Post
which one is better?

In my car, with my traffic and my roads, I found it to be a wash. I won't be setting any records for mileage, but it'll be average and I'll get in a few minutes sooner. How's that for scientific sampling? I've been getting some good numbers trying for the corridor effect. No big trucks, just me in a line of cars.

I've been in a rush way more often than is healthy lately, always either looking at a great tank until something happens or being in a a blazing rush and then spending the rest of the week trying to salvage the tank. So with sporadic higher speeds, I've been doing the best I can with found aeromods and holding my tank averages steady.

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Old 06-13-2014, 10:45 AM   #7 (permalink)
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I prefer drafting because you get to go faster, and other drivers are less pissed off by slow driving or pulse and gliding. Big rigs aren't the best to draft unless you have an SUV because they're tall and kick up a ton of rocks, but if you can find a moving truck or an otherwise very fat vehicle with normal levels of ground clearance that's best.
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Old 06-13-2014, 12:10 PM   #8 (permalink)
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I've posted many times before that I can draft at 65-70 on I64, or dirve along on route 60 at 55 MPH and get the same mileage. I don't use engine off so the coasting mileage is higher which offsets the pulse losses. I can pulse to 2 stripes and glide to 5 or more depending on the grade without other traffic being affected. If they are they are tailgating me and soon pass in the left lane.

The drafting part is when traffic gets to a point in density, drafting is unavoidable when average separations get less than 4 car lenghts (80 feet). I prefer 130 feet, but after that you get cars using the gap to pass others to the right which is dangerous and stupid.

I'll pulse up to 2 lengths then coast for along time without my speed changing by more than 10 MPH total, all the time with cars passing me in the left lane, which helps my draft even more.

When it really gets great is when the average speed of the traffic drops down to 55 but is not osciallating too badly, then I have seen mileage as high as 62 MPG in the Fiesta, but in that case everything was nearly perfect, averaging 55 MPH at 60 MPG in car rated at 38 highway.

Let the unwashed SUCK me down the highway, while I laugh when I pass them at the gas station.


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Old 06-13-2014, 12:50 PM   #9 (permalink)
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I always had trouble drafting trucks for to long , I try but the speeds get to high and I drop off, sadly out of their wind break but I refuse to drive 70mph as it raises the rpm above my mpg comfort zone which is 2000rpm max at hwy speed.

I only go below the posted speed limit if its a double lane so the less economical can pass at will , I definitely avoid disrupting others on the road.
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Old 06-13-2014, 03:52 PM   #10 (permalink)
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I tested this in the Odyssey. 65 mph drafting 2 seconds back was the same as 60 mph solo. So... 55 mph would be even better than either.

No drafting for me. Too many things can happen suddenly.


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