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Old 10-25-2014, 11:34 AM
 
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No, it doesn't make up for it, due to drag & rolling resistance.

Quote:
Originally Posted by Cape Cod Todd View Post
With gas economy Slow and steady wins the race. If you gun it to get up the hill you will use more gas than if you are just maintaining your speed.

I once heard that if you use cruise control you actually use more gas. Does that make sense?

Slow (the speed limit) and steady is the key.
On hills, cruise control uses more gas than your foot. However, one must remember that most roads are not hills. Interstate highways have a maximum grade of 6%, which is only 3.4 degree angle. On all highways, cruise control will be superior.

Last edited by Opin_Yunated; 10-25-2014 at 11:43 AM..
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Old 10-25-2014, 11:46 AM
 
Location: We_tside PNW (Columbia Gorge) / CO / SA TX / Thailand
34,559 posts, read 57,471,708 times
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Quote:
Originally Posted by Pughnose View Post
Yeah, I don't think the math would give you a perfect equality.



If I remember correctly, the energy dissipated by the brakes (through friction, producing heat) comes from potential energy being converted to kinetic energy by the acceleration of gravity. But I was not the very best of physics students.

...
Sir Isaac is smiling upon you!
Newton’s First Law of Motion: An object in motion will remain in motion unless acted upon by an external force.

Newton's 1st Law of Success: Perpetual Motion - Successify!

Conclusion

As Newton taught us, our life will head in the direction we set for it. If we aren’t careful, other factors will enter and try to pull it down or to a stop. We need to apply constant pressure in the right direction or alter the course if we see it veering away from our intended goal. Apply Newton’s 1st Law of Motion, or as I call it, “Newton’s 1st Law of Success” and you will have a lot more successful days.


Thus...I'm a firm believer in Newton, AND in HHV (Hydraulic Hybrid Vehicle). My 52 MPG grease burner will be getting my first application of HHV, and while I am COASTING I will be 'charging' my Hyd Accumulator for 'Release' at that opportune point in the future. (When I am forced to a complete stop...seldom). The HHV technology is most used in Heavy trucks (Garbage, Bus, Fire) and Australia is leading this development (I didn't know they even had hills! ) I live on a mtn, so I will get HHV 'charged' every trip to town (seldom).

But NEVER will my Charge = my required energy to get home. Sir Isaac had to prove that...

All said... my Diesels LOVE to Hyper mile... they use LITTLE fuel at idle. I coast most the way to town (99+ mpg).. then I have to drive home. (up hill) by the time I get there, I am back to only 52 mpg.. the same ole story every day
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Old 10-25-2014, 02:10 PM
 
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A good example that you do not save an equal amount of fuel going down as the extra used when going up, is when driving in mountain terrain with about equal up and down grade, you will use more fuel than driving on level ground.
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Old 10-25-2014, 02:14 PM
 
Location: Sector 001
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Wind resistance is a factor... road bikers know you dont get all that momentum back from going downhill because wind resistance increases with speed... its why a person burns a lot more calories going 22 mph vs 15 mph.

Similarly a strong crosswind will affect a road biker's speed just like it will affect gas mileage.
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Old 10-25-2014, 03:58 PM
 
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The closer to WOT on a gasoline engine, the more efficient it is. So going up a hill you are using less fuel for the work done, in theory. High mileage'ers use the "pulse and glide" method.
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Old 10-25-2014, 04:55 PM
eok
 
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The real answer is that what you get from going downhill depends on how old you are. Are you over the hill?
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Old 10-25-2014, 07:09 PM
 
Location: BMORE!
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No, the engine would rev just as high going downhill as it would going uphill since the transmission is using a high gear to keep the car's brakes from fading and losing stopping power. You keep the car from revving so high when going downhill, you'd have to (ironically) hit the accelerator.
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Old 10-25-2014, 09:01 PM
 
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Lets say your average MPG was 25 (highway) before your encountered the hill.
Going uphill your MPG drops to 15.
When you start going downhill try to maintain the speed at which your vehicle registers 35 MPG or higher. By doing so, you just recovered the 10 MPG lost going uphill.
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Old 10-25-2014, 11:53 PM
 
Location: McKinleyville, California
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Quote:
Originally Posted by gtt99 View Post
Lets say your average MPG was 25 (highway) before your encountered the hill.
Going uphill your MPG drops to 15.
When you start going downhill try to maintain the speed at which your vehicle registers 35 MPG or higher. By doing so, you just recovered the 10 MPG lost going uphill.
I noticed the same with our Honda accord hybrid, up hill the electric assist would engage along with the engine and down hill the transmission produced electricity to recharge the batteries while the engine shut down to 3 cylinders. As one poster said, slow and steady wins the race, with the Accord hybrid, a steady speed limit produced the best mileage. Max was 39 mpg for a 300 mile trip with some highs in the low 40's and lows in the mid 20's. With brake, wheel and transmission regenerative technology, much of the power used is recovered when down shifting or braking.
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Old 10-26-2014, 09:10 AM
 
41,815 posts, read 50,775,139 times
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Quote:
Originally Posted by gtt99 View Post
Lets say your average MPG was 25 (highway) before your encountered the hill.
Going uphill your MPG drops to 15.
When you start going downhill try to maintain the speed at which your vehicle registers 35 MPG or higher. By doing so, you just recovered the 10 MPG lost going uphill.
That won't work, let's say you accelerate from 0 to 60 for 1/4 of a mile on flat terrain hitting 60 right at the bottom of the hill. You maintain 60 miles an hour going up a 1/2 mile hill. When you hit the apex of the hill you turn the car off and coast down the other side, when you get to the bottom of the hill you need to coast for another 1/4 of mile and that's not going to happen.

The slopes and road distances don't really matter as long as your starting and ending points are on a plane and the exact same linear distance from the apex.
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