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 > Mileage observations

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4x4ord

Alberta

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Posted: 10/31/19 07:55am Link  |  Quote  |  Print  |  Notify Moderator

I get about 20% more mpg in Canada than I do in the US.[emoticon]


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ajriding

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Posted: 10/31/19 05:07pm Link  |  Quote  |  Print  |  Notify Moderator

Lower rpm is usually better mpg, but there are many variables in the ECU that can affect this.
If you drove a simple two cycle engine, then yes, lower equals less fuel, but on vehicles the computer changes fueling, timing, the vacuum changes, and the gears change.

In general overdrive is not an efficient gear, the gear right under it is usually the most efficient gear in the transmission, and usually translates to the most efficient at the pump (assuming speeds are appropriate for the selected gear).
In OD you cover more ground for the same engine rpm so you may get better mpg, but when towing you may not. Many variables.

In a manual transmission, in a 5 speed for ex, 5th is an OD gear, and 4th is what is referred to as a one to on or 1:1 gearing. For every one rotation of the engine the drives shaft rotates once. This literally means that the gears in the transmission are not even used, they are bypassed, not turning. The "input shaft" is locked directly to the "output shaft", so really there is no mechanical loss from the transmission. This is why it is the efficient gear (because it really is not a gear).

Similar gearing will happen in an auto trans.

The biggest factor still is how the engine fuels at different rpms and at different loads. You may find you get worse mpg at too slow of a speed and this is the engine fueling differently. 55 is typically the sweet spot, but it is worth a few bucks extra to go a little faster when you do the math.

Grit dog

Black Diamond, WA

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Posted: 11/01/19 08:37am Link  |  Quote  |  Print  |  Notify Moderator

Lynnmor wrote:

ShinerBock wrote:

Thirty minutes is cutting into my valuable beer drinking and relaxing time.


I won't tow 74 MPH for a beer.


I would!
Desperate times call for desperate measures man!


"Yes Sir, Oct 10 1888, Those poor school children froze to death in their tracks. They did not even find them until Spring. Especially hard hit were the ones who had to trek uphill to school both ways, with no shoes." -Bert A.

4x4ord

Alberta

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Posted: 11/01/19 08:56am Link  |  Quote  |  Print  |  Notify Moderator

It takes a certain amount of horsepower to pull a trailer down the highway at 65 mph. In the case of the op it might be around 95 hp. When the engine is making 95 hp and running say 4000 rpm the torque it is generating is: torque = 5252 x 95/4000 = 125 lbft of torque. If the op gears up such that the engine is running 2000 rpm the required engine output is still only 95 hp but now the torque level is 250 lbft. With the engine running at 2000 rpm there is less energy lost at 2000 rpm but more significant is the fact that the higher torque means higher cylinder pressure and more efficient burning. Slowing the engine down for the same hp requirement always causes higher cylinder pressure.

philh

Belleville MI

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Posted: 11/01/19 09:23am Link  |  Quote  |  Print  |  Notify Moderator

ShinerBock wrote:

A few years ago, I had to follow my father who only does 60 mph. It was annoying to drive that slow. After doing the math I saved less than $6 and arrived over half an hour later than I normally do.

23 minutes later assuming the entire trip was at 60mph.

Lantley

Ellicott City, Maryland

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Posted: 11/01/19 09:47am Link  |  Quote  |  Print  |  Notify Moderator

philh wrote:

ShinerBock wrote:

A few years ago, I had to follow my father who only does 60 mph. It was annoying to drive that slow. After doing the math I saved less than $6 and arrived over half an hour later than I normally do.

23 minutes later assuming the entire trip was at 60mph.

I don't doubt your math but it probably felt like an hour ...
Sorry 60 on the interstate when other traffic is doing 70-75 is too slow.


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bstar1952

Bandera, Texas

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Posted: 11/02/19 10:27am Link  |  Quote  |  Print  |  Notify Moderator

Another observation on mileage. We just returned from a trip towing from San Antonio, TX, to Colorado Springs. The entire trip north I got 10.5 to 11.2 mpg towing my 7800lb TT with my F-150. Needless to say, I was very happy camper, thinking that the more I "broke-in" my truck I was getting better gas mileage. However, I was brought back to reality on our return trip home when I was getting 6.4 to 8.5 mpg. Seems that having a strong tailwind vs. driving into the wind does make a huge difference. BTW, my sweet spot towing is 63mph. I was amazed at how many TTs and 5th wheels passed me doing well over 70mph. I pretty sure most had speed rated trailer tires. Wonder if speed had anything to do with the "more that several" RV pulled over for flats?


Bstar1952
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Lynnmor

Red Lion

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Posted: 11/02/19 11:41am Link  |  Quote  |  Print  |  Notify Moderator

I tow 63 as well and find it to be not a problem with traffic, yes the ego types might have a problem. I even travel I70 & I68 in MD quite often where the crazy drivers believe in drive left, pass right. My fuel, my equipment, my safety, so my choice.





Groover

Pulaski, TN

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Posted: 11/02/19 01:48pm Link  |  Quote  |  Print  |  Notify Moderator

Lynnmor wrote:

I tow 63 as well and find it to be not a problem with traffic, yes the ego types might have a problem. I even travel I70 & I68 in MD quite often where the crazy drivers believe in drive left, pass right. My fuel, my equipment, my safety, so my choice.


It is amazing how many people take the speed limit as a challenge instead of an actual limit. Of coarse we did have the case a few years ago where a person was charged with obstructing traffic for not going far enough over the limit and had to pay the fines.

hotpepperkid

Kingman AZ

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Posted: 11/04/19 08:07am Link  |  Quote  |  Print  |  Notify Moderator

ajriding wrote:

Lower rpm is usually better mpg, but there are many variables in the ECU that can affect this.
If you drove a simple two cycle engine, then yes, lower equals less fuel, but on vehicles the computer changes fueling, timing, the vacuum changes, and the gears change.

In general overdrive is not an efficient gear, the gear right under it is usually the most efficient gear in the transmission, and usually translates to the most efficient at the pump (assuming speeds are appropriate for the selected gear).
In OD you cover more ground for the same engine rpm so you may get better mpg, but when towing you may not. Many variables.

In a manual transmission, in a 5 speed for ex, 5th is an OD gear, and 4th is what is referred to as a one to on or 1:1 gearing. For every one rotation of the engine the drives shaft rotates once. This literally means that the gears in the transmission are not even used, they are bypassed, not turning. The "input shaft" is locked directly to the "output shaft", so really there is no mechanical loss from the transmission. This is why it is the efficient gear (because it really is not a gear).

Similar gearing will happen in an auto trans.

The biggest factor still is how the engine fuels at different rpms and at different loads. You may find you get worse mpg at too slow of a speed and this is the engine fueling differently. 55 is typically the sweet spot, but it is worth a few bucks extra to go a little faster when you do the math.


Gear ratios for the Ford 6R140 1=3.974/2=2.318/3=1.516/4=1.149/5=0.858/6=0.674
I tow a 11,000 lb 5er at around 68 on the interstates and it runs in 6th gear. I will down shift to 5th to longer hills but doesnt on the short ones. So maybe I if lock out 6th I might get better millage??I wouldnt ever shift. Would running in a lower gear than the computer requires cause it to run hotter?


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