Fuel Milage Hills vs Flat Land

Topic: Fuel Milage Hills vs Flat Land (Read 666 times) previous topic - next topic

Fuel Milage Hills vs Flat Land

June 10, 2015, 07:20:36 pm

Well, I will start with I really do not care what it is other then looking for an issue. But I did an experiment with the coach this trip. I started out and when I drive anywhere I have mountains and they suck the MPG down. I took I 81 to I70 to I 68 to I 79. All of them have strong hills that drop the MPG about a tenth of a gallon per hill finishing up at 7.4 mpg. So, I put another section up on the sliver leaf from when I finished the hills and hit I 70 in Ohio. I found I got 8.5 mpg from Zanesville OH to the NW corner of Iowa and I am on the way back now and am taking a different route that has no hills on 80. So far I have kept the 8.5 on silverleaf over over 800 miles. I am interested to see what the effect will be on the return mountain section.

Re: Fuel Milage Hills vs Flat Land

Reply #1 – June 10, 2015, 07:34:43 pm

Don't forget to factor in headwind and ground speed. It's a complex interrelationship of variables.

Going over Killington on Route 4 will drop your fuel economy 1-2 mpg over a tankful. We have seen instantaneous mpg as low as 4 on that little bump.

Going into a headwind on 287/I40 across the flats of west Texas towards NM will do the same. As will fighting a crosswind on the return trip. You will see one day in the 9's or even 10's, the next day, with the wind, down in the 7's to 8's.

Love Ohio, especially the trek from the PA border down towards Cinci when they had the 60 mph speed limit and us having to stay in 5th gear. Our coach plus toad gets in the 10's on that leg. Similarly loafing along 281 in Texas at 55 mph.

Re: Fuel Milage Hills vs Flat Land

Reply #2 – June 10, 2015, 07:50:45 pm

Unlike most people I don't keep my tank full but buy the fuel needed to get from point A to point B using 8.6 mpg and Microsoft Street and Trips as the mileage maker between said points and seems to work out every time regardless of terrain, speed, roadkill or whatever.

Re: Fuel Milage Hills vs Flat Land

Reply #3 – June 10, 2015, 07:57:55 pm

Yes, I had the time so I set the cruise at 62 or the speed limit when it is lower. The winds have been pretty strong but from the side instead of a head wind. I think it is interesting that I got the same going east and west. I wonder what the milage will be in the mountains. I agree that there is lots of variables but I had the time and I wanted to just see what happened.

Re: Fuel Milage Hills vs Flat Land

Reply #4 – June 10, 2015, 08:43:58 pm

I start out trying to get the best mileage by driving 60 but after an hour of getting run down by every semi on the road; I go into the 75-80mph mode. And do not have any idea what mileage I am getting. I sure would like to have Dave M set up.
I bet there are no trucks running Dave down.

Re: Fuel Milage Hills vs Flat Land

Reply #5 – June 10, 2015, 09:00:22 pm

Driving from our house over Donner Pass and down to Truckee will drop mileage to 5.5 mpg, about the same as driving from San Luis Obispo up Highway 1 to Monterey, CA. Flat terrain at 55 with no headwind will bring it up to 12 mpg. Topo, winds and speed make a huge difference to our U300. Mileage determined with level coach tank dipped/measured.

Pierce

Re: Fuel Milage Hills vs Flat Land

Reply #6 – June 10, 2015, 09:21:53 pm

Want to give it a test ---try the devils ditch --ie. the New River Gorge in West Virginia , on I-64 headed West . It is a 7% + grade about 3 miles with no let up . Solid steady pull . There is always a truck of some sort on the side very over heated . My coach gets 2.2 MPG at about 40 MPH with pedal to the metal , Cool day , no problem , hot day back off accordingly . I always pull my 3/4 ton 4by4 truck and it hauling my toy . that is total pulled weight 9850 pounds . This really bites the MPG , but I live with it . Brad Metzger

Re: Fuel Milage Hills vs Flat Land

Reply #7 – June 10, 2015, 09:57:45 pm

Brad, I have run that and the one on I68. You are right about the mileage. Just an observation really as I had to drive slower so I made a game of it.

Re: Fuel Milage Hills vs Flat Land

Reply #8 – June 11, 2015, 12:08:19 am

I had a good feeling about that Sandstone Mtn I-64 grade, yes a good pull, my toy will hold 57 mph up that mountain until the last 1/4 mile, it drops to 56, Yup the 500 setting, resonator when pulling the toad does good. Fuel mileage, that is what it is, I hear everything up to 18 mpg, Who really cares ?

Re: Fuel Milage Hills vs Flat Land

Reply #9 – June 11, 2015, 01:55:00 am

Quote from: Brad Metzger – June 10, 2015, 09:21:53 pm

Want to give it a test ---try the devils ditch --ie. the New River Gorge in West Virginia , on I-64 headed West . It is a 7% + grade about 3 miles with no let up . Solid steady pull . There is always a truck of some sort on the side very over heated . My coach gets 2.2 MPG at about 40 MPH with pedal to the metal , Cool day , no problem , hot day back off accordingly . I always pull my 3/4 ton 4by4 truck and it hauling my toy . that is total pulled weight 9850 pounds . This really bites the MPG , but I live with it . Brad Metzger

Isn't America great. Seriously. It is only money.

Re: Fuel Milage Hills vs Flat Land

Reply #10 – June 11, 2015, 05:53:02 am

My 40' U320 with 400hp M11 gets about 7mpg, hills, headwinds, tail winds don't seem to matter much. I average about 65 mph.

Re: Fuel Milage Hills vs Flat Land

Reply #11 – June 11, 2015, 06:52:23 am

This MPG thing is interesting to say the least . The best MPG is always a subject that gets juicy in the camp ground . Heard some really interesting numbers about that . A guy in a SOB had a 42 footer that got 22 MPG . He ask me about my MPG and when I told him about seven on a good day he said , "you must have a engine problem " my reply was , Yep , sure do . These numbers can get stretched to what ever makes you the winner in a BS session . Fun stuff on the road .

Brad Metzger

Re: Fuel Milage Hills vs Flat Land

Reply #12 – June 11, 2015, 07:07:22 am

Well I can not run that fast. Dave. I am about 45 at the top. In my old 36 foot I was about 50 at the top. To me on this trip which is mostly driving, I decided to work on fuel mileage. The next trip will be something else I am sure. Sometimes I work to get my mph avg as high as I can over the trip. I was just surprised to see 8. Something when I am usually like more like Brad and get in the 7s.

Re: Fuel Milage Hills vs Flat Land

Reply #13 – June 11, 2015, 07:17:40 am

Does the econony button help any on flat area runs? I try to run on it most of the time thru Texas and Arkansas. DAN

Re: Fuel Milage Hills vs Flat Land

Reply #14 – June 11, 2015, 07:24:37 am

Quote from: Dan J. Stansel – June 11, 2015, 07:17:40 am

Does the econony button help any on flat area runs? I try to run on it most of the time thru Texas and Arkansas.

Here is the "Ultimate Explanation of Allison Mode Setting" by Brett Wolfe. Might help answer your question.

Econo Mode

Re: Fuel Milage Hills vs Flat Land

Reply #15 – June 11, 2015, 07:51:48 am

Tks Cajik: Must have forgot about that: however, I was in the mountains near Rapid City in econo mode and started a down run and my RPMs rose real fast. Switched out of econo mode and no more problems with high RPMS

? just saying

Re: Fuel Milage Hills vs Flat Land

Reply #16 – June 11, 2015, 07:52:02 am

Good info previously discussed: MPG

Re: Fuel Milage Hills vs Flat Land

Reply #17 – June 11, 2015, 08:11:31 am

Old joke about guys discussing fuel milage. " how do you get such good milage ? Lie about it " Sorry I had to.
Gary B

Re: Fuel Milage Hills vs Flat Land

Reply #18 – June 11, 2015, 08:53:51 am

Quote from: Gary Bouland – June 11, 2015, 08:11:31 am

Old joke about guys discussing fuel milage. " how do you get such good milage ? Lie about it " Sorry I had to.
Gary B
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Comes under "CAN YO U TOP THIS" also

Re: Fuel Milage Hills vs Flat Land

Reply #19 – June 11, 2015, 09:04:49 am

Quote from: Dan J. Stansel – June 11, 2015, 07:17:40 am

Does the econony button help any on flat area runs? I try to run on it most of the time thru Texas and Arkansas. DAN

In a word, NO. On flat ground, hat highway speed, you will be in high gear-- period. It is only at or close to WOT (Wide Open Throttle) that economy mode makes a difference. It delays downshifting and speeds upshifting. But if you are not on grades that call for downshifting, economy mode makes no difference.

The exception is in stop and go traffic IF you drive at or close to WOT.

Re: Fuel Milage Hills vs Flat Land

Reply #20 – June 11, 2015, 09:07:07 am

Quote from: Dave M – June 11, 2015, 12:08:19 am

I had a good feeling about that Sandstone Mtn I-64 grade, yes a good pull, my toy will hold 57 mph up that mountain until the last 1/4 mile, it drops to 56, Yup the 500 setting, resonator when pulling the toad does good. Fuel mileage, that is what it is, I hear everything up to 18 mpg, Who really cares ?

We seem to end up closer to 50 at the top of that mountain and that's fine with me, since we're not struggling and overheating as do many typical gasoline motorhomes. Our Cummins may have only a 400 Hp/1350 lb-ft rating, but it's perfect for us. Gotta' love our old Foretravels!!

Many people like to talk about the "real" mountains in the West, but we do have some significant steep and long grades in the East.

Re: Fuel Milage Hills vs Flat Land

Reply #21 – June 11, 2015, 09:32:13 am

Quote from: John/Pat – June 10, 2015, 08:43:58 pm

I start out trying to get the best mileage by driving 60 but after an hour of getting run down by every semi on the road; I go into the 75-80mph mode. ....... I sure would like to have Dave M set up.

Change the rear end gears, 82mph around 1950rpm. a nice 75 right around perfect 1800

Re: Fuel Milage Hills vs Flat Land

Reply #22 – June 11, 2015, 01:40:43 pm

Well, I had a headwind today and I dropped to 7.9 mpg over 150 miles then I pushed it to 68 and I dropped to 7.7 but the wind had died down. When I leave I will be in the mountains so mileage will be what it is. Hammer up and run down.

Re: Fuel Milage Hills vs Flat Land

Reply #23 – June 11, 2015, 01:55:34 pm

The front design of the GVs does make a difference in fuel mileage. NASA has even codified it (Shape Effects on Drag). We don't do long trips without the Jeep behind us and since only long trips gives you enough data to get a reasonably good idea of mileage we only have short-trip data for no-toad trips. But we averaged 10.4mpg driving about 2,000 miles from central WA through the Columbia River Gorge to Portland, OR and the I-5 and US-99 and CA-41 up to SKP Park Sierra. So a mix of mountain and flat.

I could have done better but I got carried away with the way the Banks system pulled us over the hills and around the trucks.

Craig

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