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I’ve noticed this recently in my driving. As an experiment, I lowered my highway speed from 75mph to 65mph for a couple weeks, and my gas mileage went from abou

I’ve noticed this recently in my driving. As an experiment, I lowered my highway speed from 75mph to 65mph for a couple weeks, and my gas mileage went from about 26mpg to 34mpg. Car is epa rated for 33. An enormous improvement in efficiency - that experiment has totally changed my driving habits. Knowing that, I can’t believe that I’m basically the slowest car on the road now (going 65, which is the speed limit!). Crazy to think about how much fuel we’re wasting by driving fast

londons_explore 5y ago
You can get similar fuel savings by following a big vehicle like a truck. Even at a safe following distance, the already moving air behind a truck lowers your effective speed by 20mph or so, saving 25-50% of the fuel bill. Trucks that have very little ground clearance (eg a big mudguard across the back) work best. In the extreme case, in an EV, you can end a journey with more battery than you started with if you follow a truck closely (rather too close for safety, and in perfect conditions)
- leoedin 5y ago
  How would you gain energy in that situation? Surely the EV is still expending some energy? The only way that would work is if you were going down hill. The effect of drafting though is incredible. If you're ever able to get behind a big truck on a bike, it basically becomes effortless to get up to 30mph and stay there. It's quite a thrill (just make sure you have an escape route)
- tashbarg 5y ago
  I seriously doubt those numbers (-50% fuel, energy harvesting by driving behind a truck) AND you are giving incentive to try dangerous driving. Please either back those numbers up with evidence or remove them for the sake of road safety.
  - londons_explore 5y ago
    On a flat (private) road, big container-hauling truck, 65mph, stick shift car following 20 feet behind... Put the car in neutral and you can follow for miles. You need to tap the brakes occasionally to stop yourself getting too close to the truck. That tells me no engine power is being used. Obviously it's unsafe to do on the public road for a bunch of reasons, but it really shows how good automated vehicle convoys could be for the environment if they can get close enough. Here is a video of the effects of the same airflow: https://youtu.be/xkbe2NP30Fs https://youtu.be/xkbe2NP30Fs
    - tashbarg 5y ago
      Here's mythbusters doing it: https://www.youtube.com/watch?v=lttgT1XZVvE https://www.youtube.com/watch?v=lttgT1XZVvE They estimate the savings at insane 20 feet at 20 something. Far from your claimed 100%. Could it be, that your road is not as flat as you think? That would also explain the necessary braking to not run into the truck, wouldn't it? But I couldn't agree more: let the machines do that perfectly and safe. Let's reap those sweet 25-50% increase in fuel efficiency.
      - londons_explore 5y ago
        The truck they're following there doesn't go near the ground... I suspect you really need to not have any route under the truck for the airflow for it to really work well.
roflchoppa 5y ago
Make sure to not hog the fast lane :)
- californical 5y ago
  Haha of course I stay out of the way! :)
TheSpiceIsLife 5y ago
As an emergency response to the 1973 oil crisis, on November 26, 1973, President Richard Nixon proposed a national 50 mph (80 km/h) speed limit for passenger vehicles and a 55 mph (90 km/h) speed limit for trucks and buses https://en.m.wikipedia.org/wiki/National_Maximum_Speed_Law https://en.m.wikipedia.org/wiki/National_Maximum_Speed_Law
TacticalCoder 5y ago
My driving habits are changing when I drive my wife's hybrid. There's a gauge indicating the efficiency and I always try to "beat" my best: I can do as low as 2.5 l / 100 (about 94 mpg). My gazzguzzler OTOH is not planet-friendly: about 20mpg cruising on the autobahn at 105mph / 170km/h. I plan to dump it one of these days for a (luxury) BEV. > Crazy to think about how much fuel we’re wasting by driving fast I agree. I can't help it yet but I'm working on it.

londons_explore 5y ago

You can get similar fuel savings by following a big vehicle like a truck. Even at a safe following distance, the already moving air behind a truck lowers your effective speed by 20mph or so, saving 25-50% of the fuel bill. Trucks that have very little ground clearance (eg a big mudguard across the back) work best. In the extreme case, in an EV, you can end a journey with more battery than you started with if you follow a truck closely (rather too close for safety, and in perfect conditions)

leoedin 5y ago
How would you gain energy in that situation? Surely the EV is still expending some energy? The only way that would work is if you were going down hill. The effect of drafting though is incredible. If you're ever able to get behind a big truck on a bike, it basically becomes effortless to get up to 30mph and stay there. It's quite a thrill (just make sure you have an escape route)
tashbarg 5y ago
I seriously doubt those numbers (-50% fuel, energy harvesting by driving behind a truck) AND you are giving incentive to try dangerous driving. Please either back those numbers up with evidence or remove them for the sake of road safety.
- londons_explore 5y ago
  On a flat (private) road, big container-hauling truck, 65mph, stick shift car following 20 feet behind... Put the car in neutral and you can follow for miles. You need to tap the brakes occasionally to stop yourself getting too close to the truck. That tells me no engine power is being used. Obviously it's unsafe to do on the public road for a bunch of reasons, but it really shows how good automated vehicle convoys could be for the environment if they can get close enough. Here is a video of the effects of the same airflow: https://youtu.be/xkbe2NP30Fs https://youtu.be/xkbe2NP30Fs
  - tashbarg 5y ago
    Here's mythbusters doing it: https://www.youtube.com/watch?v=lttgT1XZVvE https://www.youtube.com/watch?v=lttgT1XZVvE They estimate the savings at insane 20 feet at 20 something. Far from your claimed 100%. Could it be, that your road is not as flat as you think? That would also explain the necessary braking to not run into the truck, wouldn't it? But I couldn't agree more: let the machines do that perfectly and safe. Let's reap those sweet 25-50% increase in fuel efficiency.
    - londons_explore 5y ago
      The truck they're following there doesn't go near the ground... I suspect you really need to not have any route under the truck for the airflow for it to really work well.

roflchoppa 5y ago

Make sure to not hog the fast lane :)

californical 5y ago
Haha of course I stay out of the way! :)

TheSpiceIsLife 5y ago

As an emergency response to the 1973 oil crisis, on November 26, 1973, President Richard Nixon proposed a national 50 mph (80 km/h) speed limit for passenger vehicles and a 55 mph (90 km/h) speed limit for trucks and buses https://en.m.wikipedia.org/wiki/National_Maximum_Speed_Law https://en.m.wikipedia.org/wiki/National_Maximum_Speed_Law

TacticalCoder 5y ago

My driving habits are changing when I drive my wife's hybrid. There's a gauge indicating the efficiency and I always try to "beat" my best: I can do as low as 2.5 l / 100 (about 94 mpg). My gazzguzzler OTOH is not planet-friendly: about 20mpg cruising on the autobahn at 105mph / 170km/h. I plan to dump it one of these days for a (luxury) BEV. > Crazy to think about how much fuel we’re wasting by driving fast I agree. I can't help it yet but I'm working on it.