Explain to me how towing in 4WD yields BETTER gas mileage than 2WD?

[Engineer]

I appreciate the OP posting what he noticed but some of the comments on this thread........

*Assume Engine parameters and operation is identical
*Assume Drive conditions are identical
*Know drive train losses are higher in 4x4 then 2wd

........gives us, you will not get as good of mileage if the above statements are true. Since that is not what OP saw, one or more of the statements above is incorrect...........I put my money on the test being anything but controlled.

And this is why I don't track gas mileage, the computer read out shows ~13.7 right now.

 

[Engineer]

Sub-space gravitational waves in the time-space continuum, DARPA extreme long frequency electromagnetic wave testing or genetically modified anthophila interference

*firmly snaps up the chin strap on his tinfoil hat*

If I could I would give the TR4.org trophy of the day

 

[Yukon4Runner]

Finally, a logical response!

You're welcome Mulder.

 

[Yukon4Runner]

If I could I would give the TR4.org trophy of the day

If I hit on it then you'll probably never hear from me again.

Just a sec, brb, there's someone at the door...

 

[bimrunner]

Where did you start/end each leg? I thought I read you went from Clovis to Tahoe (or Tahoe area) and back. Even if you went all the way to Reno, the elevation there is 4500' and Clovis is at 350'. I see huge mpg diff too going too/from Tahoe from elevation change on way/way back. I know I missed something, because it wouldn't make sense unless you filled your tank before you left on the way out, had exactly the same load both ways and same fuel station was used both ways (I understand it isn't the same but CA has crappy winter fuel being swapped for summer blend right now so it can make a difference too). More curious than trying to start an argument.

 

[flyinhawaiian01]

Look at the grades of the hills you climbed. Coming vs. going is never going to be exactly the same grade, for the exact same difference, and exactly the same amount of headwind/tailwind.

Do that exact same trip 10 times, then average the numbers to come up with some actual statistical data.

And you will need to have the exact same fuel for the trip too. California may have just started swapping over to the summer blend stuff and your initial trip in 2wd could have still been on the winter crap. That alone can count for 2-3mpg, I know its about 1½mpg for me without towing anything.

Also, towing a trailer with a sizable flat front nose will see HUGE differences in drag from only a few mile-per-hour difference in headwinds. If it was 15mph headwinds going and 10mph headwinds coming back, that's enough for a 1-2mpg difference, especially when you're at 55mph.

Honestly, you have way too many variables with your "testing". Unless you can find someone with a 4runner just like yours, another trailer just like yours, and is willing to follow you a few miles back, one in 2wd, the other in 4wd, only then could you really compare the data in just one trip.

I'm not mathematician, but I still remember the basics of Statistics 243!

 

[1engineer]

Look at the grades of the hills you climbed. Coming vs. going is never going to be exactly the same grade, for the exact same difference, and exactly the same amount of headwind/tailwind.

Do that exact same trip 10 times, then average the numbers to come up with some actual statistical data.

And you will need to have the exact same fuel for the trip too. California may have just started swapping over to the summer blend stuff and your initial trip in 2wd could have still been on the winter crap. That alone can count for 2-3mpg, I know its about 1½mpg for me without towing anything.

Also, towing a trailer with a sizable flat front nose will see HUGE differences in drag from only a few mile-per-hour difference in headwinds. If it was 15mph headwinds going and 10mph headwinds coming back, that's enough for a 1-2mpg difference, especially when you're at 55mph.

Honestly, you have way too many variables with your "testing". Unless you can find someone with a 4runner just like yours, another trailer just like yours, and is willing to follow you a few miles back, one in 2wd, the other in 4wd, only then could you really compare the data in just one trip.

I'm not mathematician, but I still remember the basics of Statistics 243!

Not even 100 level lol. I have taken a lot of data and tested 100's of machines over the years and you can't determine much with two data points.

 

[JohnJerk]

93ft start

564ft end

in between are very close to equal grades of elevation gain/drop

My bad as well. I thought it was 120 miles, but after looking at logs, it was 193 miles..

Tahoe is 564 ft??

 

[jpachard]

Did you happen to get non ethanol gas when you filled up and saw the improved mileage?

 

[Engineer]

Not even 100 level lol. I have taken a lot of data and tested 100's of machines over the years and you can't determine much with two data points.

But we can make a line!

 

[bimrunner]

Tahoe is 564 ft??

Add a 0 at the end of 564...

 

[Saker]

I know that 50mph or so is the max for switching into or out of 4hi to 2hi. But I don't believe it is the max recommended speed as long as you stay in 4hi.

Definitely not the max of 50MPH for 4HI.

You can switch into 4HI at or around 55MPH, You can shift out of 55MPH at any speed according to the manual, IIRC.

Can't access my manual at present!

 

[jwkilgore]

Are you saying you drove 2WD there, then switched to 4WD for the return trip?

This is also my question, and I can't see where it has been answered. Lake Tahoe is at over 6000-ft. If you were in 2WD going up and 4WD coming back down, and you really started at under 100-ft, then a 6000-ft+ climb will make a significant difference. Especially pulling a trailer, because while climbing the trailer is all dead weight but going downhill the trailer can actually be pushing you.

Even without the total change in elevation, different directions over the same road can have a significant effect. I cross a ridge every day driving to work. In one direction is a steep climb with sharp curves top and bottom. The other side has the same total elevation change but it is an slower undulating climb with much more gentle grades. Coming in to work, I can modulate my speed climbing the gentle grade (slow down a little going up then speed back up going down the undulatiosn) then coast down the steep side at 70mph. I usually gain net MPG over the hill. Going the other direction traffic slows at the bottom curve, accelerates up the hill, then down the other side where the grade is too shallow for coasting. I lose MPG going that direction.

As soon as rain stopped, I kicked it into 2WD, and IMMEDIATELY gas mileage starts taking a hit back down to 9.5-10 MPG.

Assuming you didn't hit a significant change in grade (i.e., reach the bottom of a hill), or significant change in speed (i.e., speed up now that the rain was gone) at the same time as switching to 2WD, this statement makes me think that there may actually be something wrong with your ride. I have no idea what, but it may be something.

While driving down the road at 55mph (in 2Hi, no trailer, no wind, no slope) reset the MPG average at speed and tell us what it says. Even with all your mods it should still be approaching 20mpg.

 

[JohnJerk]

Add a 0 at the end of 564...

So like the response above, this is the reason for greater efficiency on the way home.

 

[Blitzkrieg]

When you are in 4WD HI, it forces the rotational directives of your tires to change. Sort of like water skiing, and thus increases your MPG.

When in 4WD the torque and HP actually lifts all four of the tires off the ground enough to add 10-20MPG under the right circumstances.

This is widely known in scientific circles as the "Phuckmerunning" theory and something Tesla was working on when his Edsel flew off the Swiss Alps and ironically he noted his MPG increased to about 170 MPG before the car hit the ravine 4K feet below.

Don't question physics or science, just go with the flow and run that baby in 4WD 100% of the time.

 

[itsdchz]

My trek that made the most sense to look at gas mileage was from Clovis to Placerville. I filled up in Clovis, couldn't even make it to Placerville on that tank, filled up in Sac area. That is the elevation I was referring to. Makes no sense to look at mileage going through the pass, and snow, and in a line of vehicles during stop and go.

On way home, filled up in Placerville, and made it home with 34 miles to spare. Overall that gave me nearly 60 more miles of drive WITH 4WD engaged for 187 miles of the trip. Don't know what else to tell you.

Not a controlled test, but very odd to have that much MPG gain while in 4WD. But the ethanol theory could factor in...

 

[Jhalko]

I drive to and from the mtns here a lot, like the last six weekends in a row. My house in Denver is at 5800ft and I'm basically going to 9800ft. Just taking one direction my mileage in the 4Runner readout AND scan gauge varies a solid 3-6 mpg even though my average speed is probably the same. I'm full time 4wd so that doesn't change, but I'm never surprised at how random the mileage comes in. The general flow of traffic and my willingness to try and keep up seems to be my biggest variable.

OP, you just never know... Many factors.

 

[bimrunner]

My trek that made the most sense to look at gas mileage was from Clovis to Placerville. I filled up in Clovis, couldn't even make it to Placerville on that tank, filled up in Sac area. That is the elevation I was referring to. Makes no sense to look at mileage going through the pass, and snow, and in a line of vehicles during stop and go.

On way home, filled up in Placerville, and made it home with 34 miles to spare. Overall that gave me nearly 60 more miles of drive WITH 4WD engaged for 187 miles of the trip. Don't know what else to tell you.

Not a controlled test, but very odd to have that much MPG gain while in 4WD. But the ethanol theory could factor in...

Makes way more sense now. We are in the middle of switching from winter to summer blend (makes a 10%+ difference in MPG). Also, interesting thing for you to note: a big stretch of 50 that you were on is a slight grade going up headed East (downtown sac to the grade up 50 outside of Folsom). Coming West, you had probably 30 miles of that on a slightly downward grade - minor but easily explains the MPG differential. I say all is good and right in the world once again.

 

[itsdchz]

Makes way more sense now. We are in the middle of switching from winter to summer blend (makes a 10%+ difference in MPG). Also, interesting thing for you to note: a big stretch of 50 that you were on is a slight grade going up headed East (downtown sac to the grade up 50 outside of Folsom). Coming West, you had probably 30 miles of that on a slightly downward grade - minor but easily explains the MPG differential. I say all is good and right in the world once again.

Thanks!

 

[JB.]

Good news, itsdchz.

With a presumed difference that massive, replication should be a piece of cake. A luxury many situations don't offer. Do some experimenting and report back.

You just have to be careful to perform them well. The situation is ripe for confirmation bias to creep in.