gas mileage 2WD vs 4WD

[PHAT]

I have been contemplating this for a while, and thought maybe someone here is more knowledgeable, or perhaps has done the math already.  We drive a 2009 Nissan Frontier pickup truck.  Yes, it's a fancy vehicle.  I will go ahead with the excuses...we bought it from my dad with very low mileage for the "family discount" price.  Also, we live at the top of a steep hill in a small town in the mountains (Canada) where the average annual snowfall is over 12 feet (almost 4 meters), and 25 feet (over 7m) is reasonably common.  So 4WD is needed throughout the winter to safely get around without regular use of a tow truck.

In the summer, we keep the truck in 2WD all the time.  In the winter, I tend to keep it in 4WD most of the time, however there are days when the roads are in good condition, and 2WD is sufficient.  My question is, how much does the gas mileage change between 2WD and 4WD?  Is it worth the "hassle" of switching back and forth? Or should I just leave it on 4WD until spring?  (no its not difficult to do, just flick the switch.  The hard part is remembering to flick it back next time it snows!)

[sonofsven]

This is just a guess, but probably 2-5mpg worse with 4WD.
But really, you are the best person to answer this question.
Track your mileage in the summer. Track your mileage in the winter.
What's the difference?

Zero your trip odometer, fill up the tank. Next fill up, write down your trip odometer number, say 300 miles. Now fill tank with, say 16 gallons. Divide 300 by 16, thats 18.75.
Do this every time you fill up and you'll get a good idea of your mileage.

The Frontier is very capable. I wouldn't necessarily call it fancy. But it doesn't get great mileage. I'm on my second Frontier now and I average 22 mpg, in 2WD almost all the time.

[2Birds1Stone]

Proper winter snow tires will be way more important for getting up and down your snowy/icy hill safely.

[GilesMM]

If the hassle is only flicking a switch, why wouldn’t you do it? Saves gas and wear and tear on your truck. I would only use 4WD in low gear situations requiring it, not over 35 mph.

[ChpBstrd]

I would guesstimate 3-5 mpg lower.

Maybe instead of leaving it in 4wd all winter wait until the rear tires actually start slipping to change it. This may also help you be more in tune with road conditions and aware of potentially hazardous situations. The risk isn't spinning a tire while driving uphill, it's being unable to brake or sliding into a ditch despite the 4wd. In 2wd you have a little bit of forewarning from not being able to climb the hill before you slide down it. That's your signal to ask "If it takes 4wd to climb this hill, will my brakes be able to stop me on the way back down?" and that little question could change the way you drive, versus somebody who just powers to the top unaware of how slick it is.

I'd also be worried about wearing out the transfer case in a 15 year old truck with so much full-time usage of 4wd. At a minimum it wears out your tires faster.

+1 on snow tires > 4wd because snow tires help with steering and braking.

[neo von retorch]

EDIT: Realize I read your question wrong / too fast. So I'm talking about 2 different trucks. In my case, the drivetrain losses/weight of 4WD decrease gas mileage even if you don't use it.

According to Fuelly, where I tracked this, my 2014 Silverado 4WD got an average of 15.9 mpg, while my 2015 Silverado RWD got 17.6 mpg. Both were 5.3L engines.

In gallons per 100 miles that 6.29 gphm and 5.68. The difference is nearly 11% more gas to power the 4WD. (And yes it was in RWD 98% of the time.)

My dad also owned two very similar GM trucks with 4WD and RWD, and found the RWD got ~2 mpg more. He still managed to nurse his 4WD regular cab Silverado to about 18mpg though!

[SmashYourSmartPhone]

Is it worth the "hassle" of switching back and forth? Or should I just leave it on 4WD until spring?

The concern is not gas mileage, it's tire and drivetrain wear.  You may have noticed that it's harder steering on dry roads with 4WD engaged, and that is because most trucks don't have a center differential - the difference in path length when turning between the front and rear wheels is made up in tire slip when in 4WD, which is hard on the tires on dry pavement, and "winds up" the drivetrain torsionally, which is hard on all parts of it.

Use 2WD on dry roads, use 4WD on slick roads.  And get in the habit of switching as needed, don't just leave it in 4WD constantly, unless you like replacing tires and drivetrain parts sooner than required.

Track your mileage in the summer. Track your mileage in the winter.
What's the difference?

Substantial, and it doesn't involve the difference between 2WD and 4WD in the slightest.  Cold weather uses more energy to get a vehicle around - the oils are thicker in the driveline and rolling drag is substantially higher, plus the engine has to expend more energy to get up to efficient operating temperature, often people let the engine warm up longer in the winter (which is good for the engine, though you should be in the habit of warming it up some even in warmer weather), etc.

[PHAT]

This is just a guess, but probably 2-5mpg worse with 4WD.
But really, you are the best person to answer this question.
Track your mileage in the summer. Track your mileage in the winter.
What's the difference?

Zero your trip odometer, fill up the tank. Next fill up, write down your trip odometer number, say 300 miles. Now fill tank with, say 16 gallons. Divide 300 by 16, thats 18.75.
Do this every time you fill up and you'll get a good idea of your mileage.

The Frontier is very capable. I wouldn't necessarily call it fancy. But it doesn't get great mileage. I'm on my second Frontier now and I average 22 mpg, in 2WD almost all the time.

I used to track my mileage religiously, but now that I have kids, and share vehicles more with hubby, it's harder to do!  I know my (much more mustachian) 2010 Toyota matrix gets pretty much 6.5L/100km.  I know the truck is much worse, but I haven't tracked it.  Thanks for the real-world values for 2wd though!

[PHAT]

Proper winter snow tires will be way more important for getting up and down your snowy/icy hill safely.

We have top-of-the-line winter tires recommended by our local experts who are familiar with the terrain.  4WD is still required when you are driving up steep hills with 6" or more of snow on them.  I realize that 4WD does nothing for stopping, the problem is moving without getting stuck!

[PHAT]

If the hassle is only flicking a switch, why wouldn’t you do it? Saves gas and wear and tear on your truck. I would only use 4WD in low gear situations requiring it, not over 35 mph.

We have 2 options for 4WD...4HI is for any speeds, including highway driving if required.  4LO is for very low speeds only.  I'm referring to 4HI in this case, 4LO would be reserved for basically once you are stuck, or for un-stucking someone else :)

[PHAT]

EDIT: Realize I read your question wrong / too fast. So I'm talking about 2 different trucks. In my case, the drivetrain losses/weight of 4WD decrease gas mileage even if you don't use it.

According to Fuelly, where I tracked this, my 2014 Silverado 4WD got an average of 15.9 mpg, while my 2015 Silverado RWD got 17.6 mpg. Both were 5.3L engines.

In gallons per 100 miles that 6.29 gphm and 5.68. The difference is nearly 11% more gas to power the 4WD. (And yes it was in RWD 98% of the time.)

My dad also owned two very similar GM trucks with 4WD and RWD, and found the RWD got ~2 mpg more. He still managed to nurse his 4WD regular cab Silverado to about 18mpg though!

Yes, this is what I was finding when I tried to look up the answer online.  We have the heavier truck already, so the lower mileage is already a given!

[SmashYourSmartPhone]

I realize that 4WD does nothing for stopping, the problem is moving without getting stuck!

This is wrong on most trucks and just about most full time AWD cars, but it persists as a cute pithy saying.  What is the term for "Sounds true but is in fact wrong?"  Truthy?

Go try it.  You will stop faster in 4WD.  You simply lose stability when you lock the tires, if you don't have antilock.

Any modern vehicle will bias braking force to the front, as this is what's effective when you have normal weight transfer - the front tires load up and can take more braking force, the rear unloads and needs less brake force.  Plus, typically, you find larger discs in front, and either drums or smaller discs in the rear.  The braking power is far from distributed 50/50 between front and rear.

On snow, this system has the advantage of keeping the rear wheels turning for stability, but as you don't get much weight transfer under slower snow deceleration rates, the rear is substantially underbraked compared to traction.

With a typical truck-type 4WD system in which the front and rear are locked together with no center differential, this allows braking force to slow all four tires equally, and you get rather substantially better braking as long as you avoid the condition in which you lock all four tires (I assume modern antilock systems work with this case, I don't have anything with modern antilocks and 4WD to try it on).

Seriously, find a parking lot and try it.  You'll be surprised at the difference.

But, hey, it sounds good, right?

[PHAT]

Is it worth the "hassle" of switching back and forth? Or should I just leave it on 4WD until spring?

The concern is not gas mileage, it's tire and drivetrain wear.  You may have noticed that it's harder steering on dry roads with 4WD engaged, and that is because most trucks don't have a center differential - the difference in path length when turning between the front and rear wheels is made up in tire slip when in 4WD, which is hard on the tires on dry pavement, and "winds up" the drivetrain torsionally, which is hard on all parts of it.

Use 2WD on dry roads, use 4WD on slick roads.  And get in the habit of switching as needed, don't just leave it in 4WD constantly, unless you like replacing tires and drivetrain parts sooner than required.

Track your mileage in the summer. Track your mileage in the winter.
What's the difference?

Substantial, and it doesn't involve the difference between 2WD and 4WD in the slightest.  Cold weather uses more energy to get a vehicle around - the oils are thicker in the driveline and rolling drag is substantially higher, plus the engine has to expend more energy to get up to efficient operating temperature, often people let the engine warm up longer in the winter (which is good for the engine, though you should be in the habit of warming it up some even in warmer weather), etc.

Good advice thank you.  I do try to change to 2WD if we have a dry spell for several days and the roads are nice and clear.  The problem with living in the mountains is that weather conditions change so quickly!  It can be icy winter up here at the top, and basically summer just a few kilometres down the road at lower elevations!  And switching back and forth is a bit tricky to do WHILE driving, because I think it will only change below a certain speed (I haven't paid that close attention to the details, but I do notice that when I switch from 4 to 2, it doesn't always go right away)

The turning radius is definitely affected, I often switch to 2WD if I need to go into a parking lot or somewhere tight.  Good to know about the wear and tear on the drive train, that sounds expensive, so probably worth paying closer attention just for that!

[innkeeper77]

Is it worth the "hassle" of switching back and forth? Or should I just leave it on 4WD until spring?

The concern is not gas mileage, it's tire and drivetrain wear.  You may have noticed that it's harder steering on dry roads with 4WD engaged, and that is because most trucks don't have a center differential - the difference in path length when turning between the front and rear wheels is made up in tire slip when in 4WD, which is hard on the tires on dry pavement, and "winds up" the drivetrain torsionally, which is hard on all parts of it.

Use 2WD on dry roads, use 4WD on slick roads.  And get in the habit of switching as needed, don't just leave it in 4WD constantly, unless you like replacing tires and drivetrain parts sooner than required.

Track your mileage in the summer. Track your mileage in the winter.
What's the difference?

Substantial, and it doesn't involve the difference between 2WD and 4WD in the slightest.  Cold weather uses more energy to get a vehicle around - the oils are thicker in the driveline and rolling drag is substantially higher, plus the engine has to expend more energy to get up to efficient operating temperature, often people let the engine warm up longer in the winter (which is good for the engine, though you should be in the habit of warming it up some even in warmer weather), etc.

Exactly. Driving in 4WD in a frontier is actually the same as a driving more expensive 4x4 (think land cruiser) with the center differential lock on at all times. Not great, VERY high wear on the drivetrain even if you don't pop something- which is certainly possible. They aren't made of glass of course, but over time damage adds up. It's kind of like a less extreme version of driving on pavement with your rear locker engaged- a bad bad idea.

This will also cause increased tire wear, which in addition to being expensive, will shed a higher amount of microplastics than normal.

Just try and remember to keep switching it. Shouldn't you be able to switch between 2WD and 4High at speed?

PHAT: I agree! Interestingly, being in gear and 4WD can actually IMPROVE braking! Slightly. Not enough to really say it is a thing.. but locking the front and rear together can actually help transfer braking power to where it is needed! There are some youtube tests of this. Also, with enough snow, using 4WD can make keeping traction- avoiding kicking the back end out- a lot easier. I also would say if you find yourself at 55 or over for much time at all, safely, you probably have plenty of traction and can drop down to 2WD. (Edit: A much better explanation of this is above!)

These vehicles are terribly un-mustachian, but I use mine for some SAR volunteering so it is worth it to me. Don't increase wear and maintenance and cost and environmental impact even more just to avoid having to think about the selector!

[innkeeper77]

And switching back and forth is a bit tricky to do WHILE driving, because I think it will only change below a certain speed (I haven't paid that close attention to the details, but I do notice that when I switch from 4 to 2, it doesn't always go right away)

I'd dig out a manual for your truck- it should be able to switch just fine. Mine switches slowly but better when I clutch in for a moment- the computer is running it, so it doesn't even matter much in this case if it is delayed, does it? Mine says switch only below 55, but you can take 4High up to any speed, you just need to slow down below 55 before it will actually switch in or out of it. (Different brand and everything though, your mileage may vary)

[SmashYourSmartPhone]

And switching back and forth is a bit tricky to do WHILE driving, because I think it will only change below a certain speed

Why don't you read the manual on your vehicle and find out how to actually operate it according the guide written by the people who built it, instead of guessing?

A mechanical system should slide in and out freely at any speed, the "turn a knob" style are often vacuum actuated, and popping off the gas briefly will often provide enough vacuum to snap it smartly in or out.

The turning radius is definitely affected, I often switch to 2WD if I need to go into a parking lot or somewhere tight.  Good to know about the wear and tear on the drive train, that sounds expensive, so probably worth paying closer attention just for that!

The howling of your power steering pump, tires, and engine as you fight a fully wound up drivetrain, is the howl of money departing your wallet at a rapid rate.

These vehicles are terribly un-mustachian, but I use mine for some SAR volunteering so it is worth it to me.

If they're used for their capabilities and you have a better transport for "few people, good condition roads," I can't criticize too much.  I've got a truck that gets a few thousand miles a year, almost entirely of "truck things" like heavy snow, trailer hauling, lumber, concrete, etc.  If it's empty, odds are very good I'm on my way to go pick up a few thousand pound of something.

[uniwelder]

The concern is not gas mileage, it's tire and drivetrain wear.  You may have noticed that it's harder steering on dry roads with 4WD engaged, and that is because most trucks don't have a center differential - the difference in path length when turning between the front and rear wheels is made up in tire slip when in 4WD, which is hard on the tires on dry pavement, and "winds up" the drivetrain torsionally, which is hard on all parts of it.

Besides turning, even driving in a straight line with 4WD on dry pavement is really hard on the tires and drivetrain.  In 4WD, the front wheels are geared to spin slightly faster than the rear to help climb and track straight.

[innkeeper77]

If they're used for their capabilities and you have a better transport for "few people, good condition roads," I can't criticize too much.  I've got a truck that gets a few thousand miles a year, almost entirely of "truck things" like heavy snow, trailer hauling, lumber, concrete, etc.  If it's empty, odds are very good I'm on my way to go pick up a few thousand pound of something.

I could never have it as my only vehicle, even ignoring the fuel use, trucks are terrible for cities and suburban areas for pedestrian safety and take up a lot of physical and visual space on the road. I don't commute to a job, so I am able to borrow my wifes PHEV for almost all local purposes when I need a vehicle. The cargo bike picks up the rest of the slack!

[SmashYourSmartPhone]

Besides turning, even driving in a straight line with 4WD on dry pavement is really hard on the tires and drivetrain.  In 4WD, the front wheels are geared to spin slightly faster than the rear to help climb and track straight.

Not on any truck I'm familiar with.  There's no mechanism to even do that for a minor difference, you'd have to drop a tooth on the front pinion gear, and that's more than a "slight" difference.  It'd bind horribly any time it was in use.  The center transfer case is just a locked/unlocked thing.

I'm aware some cars do a bit of a non 50-50 torque split, through methods, but I've never seen it on any truck I'm familiar with, at least.

[uniwelder]

Besides turning, even driving in a straight line with 4WD on dry pavement is really hard on the tires and drivetrain.  In 4WD, the front wheels are geared to spin slightly faster than the rear to help climb and track straight.

Not on any truck I'm familiar with.  There's no mechanism to even do that for a minor difference, you'd have to drop a tooth on the front pinion gear, and that's more than a "slight" difference.  It'd bind horribly any time it was in use.  The center transfer case is just a locked/unlocked thing.

I'm aware some cars do a bit of a non 50-50 torque split, through methods, but I've never seen it on any truck I'm familiar with, at least.

There's the pinion and the ring gear, so tighter combinations can be created if you change both.  I think they're less than 2% different front to back, but maybe that's people that do custom work on their trucks to alter the differential.  From the factory, perhaps it is 1:1, so maybe I'm getting info mixed up.