Sorry, nope. There's no 'divided by two' in the gas mileage formula you would need to use to get your average roundtrip mpg. It's a common math mistake that I run into on this forum all the time. Because that isn't how you calculate mpg at all (I'll run some numbers in a moment to demonstrate what I mean), the uphill portion of the trip, going a little while with low mileage, can actually be a much, MUCH bigger hit to FE than you imply. Mountains are not good for FE. You need far more than an equal distance at good FE to bring your average up enough to counterbalance the lost efficiency of very poor uphill legs to your trips.

Here's what I mean. Let's take the numbers you offer.
Say the distance is 2 miles up the hill and another 2 miles back down it on the way home.

Going uphill, you get 15-20 mpg for two miles. How much gas have you used? The formula is this:
Distance [miles] = FE [miles/gallon] * G [gallons]. See how the units work out?

So 2 miles = 15 *G, G = 2/15 = .1333
or 2 miles = 20 *G, G= 2/20 = .1, so somewhere between .1 and .1333 gallons of fuel burned

On the way back, you get
2 miles = 100 *G, G=2/100= .02
2 miles = 200*G, G=2/200= .01 gallons of fuel burned.

Total trip: worst case scenario, you've gone 4 miles and burned at most .1533 gallons, at best, .11 gallons.
4 miles = FE * .1533, FE= 4/.1533, FE=26 mpg
4 miles = FE* .11, FE =4/.11, FE= 36.36 mpg

Neither scenario is actually that great of an average roundtrip. Well, the high end is good for an SUV, but it stinks for an HCH. Either way it gets nowhere near the numbers you would get if your math was right. If we do as you suggest, and add them up and divide by two, we get (100 to 200) +(15 to 20)= (115 to 220), half of which is 57.5 to 110 mpg regardless of distance, which is just not correct. The actual math gets you a range for your average fuel efficiency from 26 to 36 mpg. Any distance will get basically similar results, the 2 miles part is not important to the overall point, and longer distances would just be lower. All the fuel you burn going uphill cannot be gotten back just by going back down the hill on very little fuel- the first trip still burned all the extra fuel.

See what I'm saying? So if you go up the hill at 15 mpg, and then even if you managed infinite FE on the way back down, just rolling the car with the engine off, let's say, you'd have still burned the .1333 gallons for the whole 4 mile trip, and D= FE * G, or 4 miles = FE * .1333, for a best possible FE of 4/.1333 = 30 mpg. That's the top limit, whether you are doing 60 mpg on the way back down, or 600 mpg, or 6000mpg, because you can't unburn that uphill gas.

I still say it's phenomenal that you're getting those numbers in the mountains. I have no idea what your drives are like, if there's traffic, or whatever. Maybe there are flat areas where you do most of your driving, I don't know. I didn't mean to lecture you, I just don't want to let misinformation stand because other people read these posts later.

 

Very Good Leahbeatle!

That's why I try to increase my speed slowly before coming up on a bridge here in Florida, and then try to get to the top in EV if traffic permits. On the way down, I replace much of SoC with regen keeping below 40mph where the ICE will start. Once I rob everything I can from big oil on the bridge, I throw the FEH in neutral with the ICE still off, then glide down the road laughing my XXX off at them.

Mountains can get a bit hairy I think, maybe I should stay in Forida for awhile.

GaryG

 

Geez.... of course I understand what you are saying, but you too are incorrect. What I said originally, I stand by it. It is field tested and field proven. I wasn't making a scientific statement, just a general remark. YOU are doing "in theory" and I'm describing real life. The LONGER you drive in the mountains, the better really.

Take your math: ( nothing wrong with the math, just the description )

100 miles uphill @ 25 MPG = 4 gallons burned.
100 miles downhill with engine off = 0 gallons burned.

You have gone 200 miles from 4 gallons burned = 50 MPG.
This is what I meant by "Great Results" on a mountain round trip.

Going 100 miles over flat terrain would be about 33 MPG going, and 33 MPG return which would be a 33 MPG average for the round trip.
( average driver, not hypermiler )

I've done it. Others have done it. It is PROVEN that with the FEH the more hills you have, the better, as long as you are not making really short trips on a cold engine/battery.

I "can" get 25 MPG going uphill, if the hills are in the 3% to 6% range.
I "can" get infinate MPG doing downhill if I choose roads with about 40 MPH speed limits. If you drive over 40 MPH, then a small amount of gas will be burned on the downhill trip. But since the uphill is not constant uphill, some sections do better than 25 MPG. These sections offset the small amount of gas used on the downhill, when I do go faster than 40 MPH.

No matter the exact conditions, I ALWAYS get better MPG in mountains than flat areas... even at highway speeds. I'm almost always in the 40's to 50 MPG in the mountains. Really.
It's all about energy managenment. Battery energy, gasoline energy, potential energy, kinetic energy, paying attention to momentum, etc.
I may go +10 over the speed limit on the downhill sections, and go -10 MPH on the uphill sections, getting to the destination at about the same time as with cruise control, but I'll get perhaps 20% better FE driving with "load" constant, vs. speed constant.

The bottom line, the FEH has good FE going uphill, and excellent going downhill. A standard car is poor going uphill, and just good going down.
-John

P.S. And yes, I know this goes against "conventional wisdom" but this is not a conventional car. The FEH does not break any laws of physics, but you have to look deeper, such as less energy lost to waste heat as well... things not commonly discussed.

 

Well, the real question has to be what the gasoline usage is on the downhill coast? I don't think we can use a MPG estimate to determine the true numbers rather a rate of fuel usage and the time it takes to coast down the mountain. I assume the rate of burn is the same rate of fuel consumption as the vehicle uses at idle. Does anyone know how much fuel these vehicle burn at a warm idle? We definitely can't use the onboard MPG estimates and I don't know how high the scangauge reports MPG #'s.

I think the real answer will depend on a number of factors such as the rate of climb and descent, the angle of the incline/decline, etc. I know that when I cross a large bridge, my FE is always higher when I get to the other side. I'm guessing that on alot of these mountain roads, much of the descent can be done at speeds below 40mph thus allowing for ICE shutoff. If you can get 20MPG on the way up and ICE off on the way down, you are looking at 40MPG, that is well above the EPA #'s and is excellent FE for a 3,000lb SUV...or even a regular car. In addition, even 36MPG is going to be above the typical FE of most FEH and MMH drivers and that CAN be achieved with a 20MPG climb and the ICE on during decline (by your calculations anyway).

 

Thanks for the comment Tim. I think everyone is correct in thier own way, and is adding to the "big picture". Someone else said: "I live in San Francisco and get terrible MPG with all the hills." Well, this can be true as well.

I do not think you can compare highway driving in the Rocky Mountains ( me ) with San Francisco hills in the city.

I do BIG hills with constant momentum for hours. I'm not stopping and starting every block. These are two different beasts indeed.

I guess in reality, hills can be friend... or foe.
-John

( P.S. the ScanGauge can in theory display 9999 MPG ( 4-digits ) which is what it does in EV mode. Coasting down a 6% grade at 60 MPH with engine on, it displays about 220 MPG )

 

No, John, my calculations are not 'in theory.' They are the actual formulae that relate distance, fuel efficiency, and gas burned. The numbers came from you, anyway, but they aren't important- the formula and my bigger point about the fuel lost and how much further you have to go to make up for it is still absolutely correct. Whether or not the measurements of those various numbers I plugged into the formulae are accurate is a completely different question- whether you really get 36 or 37 mpg because you're losing heat or whatever is a question for the person who develops or engineers the mpg meters. Why do we even have to go there?

As for 'conventional wisdom,' I'm not interested in stereotypes. I have a physics degree from Stanford University, and I'm interested in data. Demonstrable, repeatable, measurable numbers that you can use to compare one thing to another so that you know what you're talking about and what the person you're talking to is talking about. The example you give seems far more theoretical than anything I claimed. I mean, you pull the 33 mpg out of thin air and compare it to an average calculation you have made in which you used the rather astonishing assumption that you can travel 100 miles without using any gasoline at all. My example, where a 15 mpg trip became 30 mpg if you used no gas, involving that factor of two we were talking about, was a theoretical LIMIT, as I explained. I certainly wouldn't advocate that anyone go around driving down mountains just by rolling downhill without even being in gear- in fact, that's against the traffic laws in some states. That's just not safe. And certainly you might roll for a couple of miles- but a hundred? I know Denver is hilly, and you're gaining a lot of potential energy on your way down, of course, but I'm going to be a little skeptical.

I think it's great that you always get better mpg in the mountains than on flat ground. I think you must have perfected that particular driving technique to maximize the efficient use of the tools available to you in the FEH. I'm sure others can, too. If you have tips, by all means, post them. On that topic, thanks, GaryG!

 

John, here your saying you get 15-20mpg going uphill, and now your giving examples of getting 25mpg up a 3-5% grade. Forgive me for saying your all over the map here. Examples, theorys and such don't mean much till you post a picture of your MTE. Like Leahbeatle said, what are your techniques so we can learn. All of my hypermiling techniques are availible in my articles and any given questions to me.

The fact is, I want to find something like Wayne Gerdes showed me about neutral coasting, FAS and ridge riding. It can all be apart of normal driving, not that there'e anything wrong with that! But Big Oil has just kicked us in the face with a new increase.

GaryG

 

As you MUST know... roads are NOT a perfect gradient. Climbing from say 5,000 feet to 11,000 feet above sea level invloves sections of 1% grade, 2%, 3% grade, 4% grade, 5% grade, 6% grade, and 7% grade if I use Interstate 70 as an example.

The data support that a 7% grade at 60 MPH will yield about 15 MPG.
A 1% grade will net about 35 MPG at 60 MPH.
You smart guys can figure out the rest in between. I'd hate to bore you.

A particular route up from 5,000 feet ASL to 11,000 feet ASL will average 25 MPG. The same route down will net 125 MPG.
The route is about 75 miles each direction.

ACTUAL RESULTS from a RECENT WINTER TRIP:

75 miles @ 25 MPG (ave.) = 3.0 gallons used. Average speed = 60 MPH
75 miles @ 125 MPG (ave.) = 0.6 gallons used. Average speed = 60 MPH

150 miles ( round trip ) from 3.6 gallons used = 41.67 MPG
WHO HERE SAYS 41.67 MPG is not a great end result?

Actual results from another summer trip:
Start, 4900 ft ASL. Destination, 8500 ft ASL. Return to 4900 ft.
Round trip of 85.3 miles.
Rural Route, 35-45 MPH speed limits, very steep with sharp curves.
Total gas used: 1.70 gallons
RT Fuel Economy: 50.2 MPG

Look at the GreenHybrid fuel database. The average result is 31.5 MPG.
The average driver does not drive in the Rocky Mountains.
Hence, any intelligent person would conclude mountains are NOT a dis-advantage with the Ford Escape Hybrid.

If I lower my average speed to under 40 MPH by taking rural roads vs. interstates, I get middle 50's for round trips. This has been accomplished by 2 other FEH owners in the area, so there is nothing peculiar with my vehicle, my driving, or my results.

Gary,... you have no place to talk here...you live in the flattest state in the union. You have no idea what steep mountain driving is like with a FEH. You'd probably crash!!! ( and burn )
You have "bridges".
I'm sure you have mastered driving over bridges.
I have mastered steep mountains.
While you get a half mile gravity assisted coast... I get 50, 60, or 75 miles sometimes on one trip. ( with various amounts of ICE on and ICE off )

Please look here for 2 years of data.
https://www.greenhybrid.com/compare/...e/car/563.html
Please read the notes also for more insight.

Gary, you WILL see my tank MPG's are all over the place. OF COURSE! I have very DIVERSE driving conditions ( unlike you ) which have shown me more sides of the FEH and taught me more about how this car works than you will ever know. So get off your high horse before someone knocks you off, and get your nose back into reading some patent that has nothing to do with the FEH. The main thing you've shown people is how to be a dangerous driver.

All of Gary G's posts should come with the standard disclaimer car TV ads use:
Performed by a stunt driver on a closed course. Do Not Attempt.

"..neutral coasting, FAS and ridge riding... It can all be a part of ABnormal driving..."

 

gpsman1- thanks for the data! I love data! And that's some darn impressive data, too- I'm sure it's no coincidence that you rank so high in the database.

I'm not trying to criticize anyone and I hope you don't take any of this discussion that way. Good luck with any mountain driving you do, everyone! Clearly it's possible to get great FE anywhere.

P.S. I always thought Nebraska was the flattest state in the union. Oh, well.