Hypermiling

astonwest · Jul 12, 2008

I prefer driving UNDER the tractor trailer, myself.
Or on top of it, if it's a car-hauler.

astonwest · Jul 12, 2008

alittlenerdy said:
I highly doubt that your optimal performance, in terms of gas usage, is 80 MPH.

Depends on the car...if it's a German car, it may well be set up for use on the Autobahn. American car makers generally design theirs for optimum at 60 (which is the number used for the "official" testing)

Fraulein · Jul 12, 2008

Increased speed, increased air friction. It's that simple.

maestrowork · Jul 12, 2008

alittlenerdy said:
I highly doubt that your optimal performance, in terms of gas usage, is 80 MPH.

I have a sports car. I don't know about theories, but I found that my car achieves the best fuel efficiency at around 75-80 mph. I once reached about 41 mpg on a long stretch of highway going at about 75 mph. I did 430 miles with one tank of gas.

That's why I say go with your car's optimal speed. You'll have to experiment.

Fraulein · Jul 12, 2008

Have you ever done a gas mileage log? It's difficult to eliminate extraneous variables, but it's worth a shot. See what your gas mileage is at 55 MPH, 60 MPH, 65 MPH, etc. on longer trips and compare the results. My bf and I find that it is easier to gauge gas mileage right after the tank is filled up, and we always reset the trip odometer after a fill up.

Sports car or not, the faster you go, the more friction (drag) you will create.

The dynamics of your car would have to out of this world if your gas mileage was better at 80 MPH than 60 MPH. The lowest drag is almost always associated with a sphere or tear drop shape, hence the Honda Insight hybrid (70 MPG) looks like a tear drop. Unless you're driving one of those, I would assume that you're creating more drag than is desirable at higher speeds.

Also, here's a short, to the point article if you would like to read it.

maestrowork · Jul 12, 2008

Extreme hypermiler, getting 59 mpg out of a Honda Accord:

http://www.motherjones.com/news/feature/2007/01/king_of_the_hypermilers.html

Now, he sounds a bit reckless to me...

maestrowork · Jul 12, 2008

alittlenerdy said:
Have you ever done a gas mileage log? It's difficult to eliminate extraneous variables, but it's worth a shot. See what your gas mileage is at 55 MPH, 60 MPH, 65 MPH, etc. on longer trips and compare the results....

The dynamics of your car would have to out of this world if your gas mileage was better at 80 MPH than 60 MPH. The lowest drag is almost always associated with a sphere or tear drop shape, hence the Honda Insight hybrid (70 MPG) looks like a tear drop. Unless you're driving one of those, I would assume that you're creating more drag than is desirable at higher speeds.

Yes, over the last few years I have done extensive gas mileage log and that's how I found out that my best mileage is at around 75-80 mph. I do have a sports car, so perhaps its aerodynamic is optimized at a higher speed. At around 88 mph with a maximum torque at 4400 RPM (now it sounds like Back to the Future...). I don't know if it's a coincidence but that's what I found out after studying my logs.

astonwest · Jul 12, 2008

alittlenerdy said:
Sports car or not, the faster you go, the more friction (drag) you will create.

Yes, but every car has a "sweet spot" which is more dependent on torque than speed.

The dynamics of your car would have to out of this world if your gas mileage was better at 80 MPH than 60 MPH.

I have a friend who is big into SCCA racing, and knows far more about engines, tuning improvements, etc. than I do. He made the same claim regarding a BMW he just sold. It's not that outrageous a claim if a car was optimized for higher speeds, and you drive it slower.

The lowest drag is almost always associated with a sphere or tear drop shape, hence the Honda Insight hybrid (70 MPG) looks like a tear drop. Unless you're driving one of those, I would assume that you're creating more drag than is desirable at higher speeds.

Drag is only one part of the total equation. Although you are correct that [profile] drag is lower with a sphere or tear drop (airfoil), required power (and thus fuel consumption) is also based on weight, number of cylinders (Honda CRX, anyone?), and torque at a particular speed, among others. There are numerous variables involved...

maestrowork · Jul 12, 2008

Ah car talks. Like the old times (I belonged to a car board).

Joycecwilliams · Jul 13, 2008

Thanks Maestro...

I live in NH and we have lots of hills, and it's easy to coast down, but hard to get up. I was coasting down a hill yesterday at 50 miles an hour and was stopped for speeding. Gee I hate putting on the brakes when I am picking up speed.

Thank God and thanks to the policeman I didn't get a ticket, it would have been $75.00 for goint 50 in a 35 mph zone.

maestrowork said:
Does anyone here practice that? For those who don't know the term: hypermiling is a way of driving to conserve energy and gas usage, mostly often at the expense of speed.

What do you think?

I've been doing that in the past couple of years and I'm now constantly getting 38 mpg (and I have a sports car with a published gas mileage as 28/32). I'm very pleased with the results. The biggest gain for me is by using the cruise control extensively -- by letting it control the gas it does a much greater job than humans can.

What I do:

- use cruise control anytime I'm not in stop-and-go traffic or under 35 mph.
- coast to stop, sometimes shift to neutral
- coast whenever necessary, especially on downgrades
- ease from a start instead of stepping hard on the accelerator
- maintain a constant speed (thus the cruise control)
- turn off the A/C and just put the top down or lower the windows
- make sure my tire pressures are at the optimal
- keep the car in good shape (it's over six years old now)

If you're in the market for a new car or you're considering getting cruise control installed, get it. Not only is it easier and safer on highways, it's also a major contributor to hypermiling.

The only thing I don't do is staying at speed limit. I usually like to be about 5 miles above the limits. Personally I don't see how the speed limits would factor into this. I think one each car is different. Mine is at its optimal performance at 80 mph, so driving at 55 or 65 doesn't really make sense.

Hypermiling

astonwest

2 WIP? A glutton for punishment

astonwest

2 WIP? A glutton for punishment

Fraulein

Spooks? Where are you?...

maestrowork

Fear the Death Ray

Fraulein

Spooks? Where are you?...

maestrowork

Fear the Death Ray

maestrowork

Fear the Death Ray

astonwest

2 WIP? A glutton for punishment

maestrowork

Fear the Death Ray

Joycecwilliams