BeachLeaf
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Most Efficient Freeway Speed...Is There One?

Tue Apr 30, 2019 4:05 pm

Hi all, on a recent road trip and riddled with range anxiety from not having made the trip before, I wondered if anyone has found what the most efficient highway/freeway speed is?

That is, is there a notable difference from going 55 MPH vs. 65 MPH when considering distance?

Thanks,

Mark
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LeftieBiker
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Re: Most Efficient Freeway Speed...Is There One?

Tue Apr 30, 2019 4:34 pm

The most efficient speed is something like 17MPH. That being said, 55MPH is definitely better than 65MPH, and 40-45MPH works well on secondary roads . Since the indicated speed is 2MPH high, I usually set (on my old 24kwh Leaf) the cruise control to 57MPH, and let it drop to 50 on uphills. The bottom line: if you need to extend range, go as slowly as traffic safely allows. If you have to go fast, try getting 4 car lengths behind a tractor-trailer, matching speeds, and drafting it. That isn't extremely safe, however...
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webeleafowners
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Re: Most Efficient Freeway Speed...Is There One?

Tue Apr 30, 2019 5:37 pm

In the Okanagan Valley there are few speed limits over 90 kmh. And the Mounties live their speed traps. Sooooo, we spend a lot at around 90 to 95 kmh. Our GOM is typically more than 190 on a full charge and it’s accurate. So yah. I would say 55 mph is quite a bit more efficient.

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jjeff
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Re: Most Efficient Freeway Speed...Is There One?

Tue Apr 30, 2019 6:12 pm

As Leftie said, the slower the better but of course you don't to be the only one going 50 or 55 if everyone else is doing 70mph. I've noticed a much faster drop in charge going over 60 so if you can do 55 that would probably be best if traffic allows, 60 if not. With the Leaf(and probably all EVs) side roads where the speed is slower is better than freeway speeds, even if you have to stop for signs or lights.
EVs really shine in stop and go traffic, getting better than 70 with no traffic, when driving my EV it's the one thing positive to say about slow traffic :)
70 is a real range killer but if I have plenty of charge or a short distance the Leaf handles 70+ just fine, just kills range.
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alozzy
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Re: Most Efficient Freeway Speed...Is There One?

Tue Apr 30, 2019 7:12 pm

The force of the air slowing the car down varies by the square of the velocity, so the speed of the vehicle has a huge impact on efficiency.

For example, 50 mph is about 22.4 m/s and 60 mph is about 26.8 m/s, do the math and, all other things being equal, you'll find that 10 mph change increases air drag force by 43%
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TomT
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Re: Most Efficient Freeway Speed...Is There One?

Wed May 01, 2019 5:47 am

And contrary to some belief, the Leaf is not particularly aerodynamic so speed plays an even bigger part i n range...
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powersurge
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Re: Most Efficient Freeway Speed...Is There One?

Wed May 01, 2019 6:24 am

I have found that the best speed to highway traffic flow is to set the cruise control to 53-55.

That is the national speed limit. If you are on an interstate, and the speed limit is 65-70, then stay at 53, and put on your hazard lights.. You have the lawful right to go any speed you want, so let them be annoyed.

You are not going to lose to keep strangers that are speeding happy.

SanCarlosJeff
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Re: Most Efficient Freeway Speed...Is There One?

Wed May 01, 2019 9:28 am

powersurge wrote:I have found that the best speed to highway traffic flow is to set the cruise control to 53-55.

That is the national speed limit. If you are on an interstate, and the speed limit is 65-70, then stay at 53, and put on your hazard lights.. You have the lawful right to go any speed you want, so let them be annoyed.

You are not going to lose to keep strangers that are speeding happy.


The Highway Code says:

“Hazard warning lights. These may be used when your vehicle is stationary, to warn that it is temporarily obstructing traffic. Never use them as an excuse for dangerous or illegal parking. You MUST NOT use hazard warning lights while driving or being towed unless you are on a motorway or unrestricted dual carriageway and you need to warn drivers behind you of a hazard or obstruction ahead. Only use them for long enough to ensure that your warning has been observed.”

IMHO people driving 70 in a 70 zone are much safer and lawful (though not more efficient) than a car going 53.
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LeftieBiker
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Re: Most Efficient Freeway Speed...Is There One?

Wed May 01, 2019 11:19 am

IMHO people going 15MPH above the speed limit are endangering others as well. If the posted limit is 70, that's another story. In the Northeast, people usually drive much faster than the posted limit.
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powersurge
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Re: Most Efficient Freeway Speed...Is There One?

Wed May 01, 2019 12:13 pm

So what people are saying is that if the speed limit is 65, then everyone needs to do this speed (or more)?

Anyway, I found that a good number of states allow Hazard lights to be used while driving.....

https://drivinglaws.aaa.com/tag/hazard-light-use/

I think that if a person does not feel comfortable driving faster than 55, then no one has the right to critique that, no matter what the speed LIMIT is... I have the right to drive at any lawful speed I want. So, I think 55 is still good on ANY highway...

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