4x4 vs 4x2 question

Would a 4x4 in 2 wheel drive selection get the same mileage as a 4x2 (2 wheel drive only) ?

Answer, in general, is no.  A 4 wheel drive vehicle is generally heaver because of the front drive axle and transfer case, so it will generally use more gas than the same vehicle equipped with 2 wheel drive only.  Some of the newer ALL wheel drive (as opposed to a true 4X4 with a transfer case) may get close to the same mileage as their 2 wheel drive counterparts.  It just depends on the vehicle.

I agree with Dan. Comparing model to model, a four wheel drive always has more hardware to turn even in two wheel drive. Depending on the set up this extra hardware can be a lot or not very much, but it still creates some drag which has to be overcome at the cost of fuel economy.

Agree with the others - the transfer case in a 4x4 always soaks up some extra energy, regardless of mode. However, fuel economy should be lightly better in 2WD v 4WD mode.

OTOH, you only need to get stuck and pay for a tow truck once and you  will have more than paid for the difference in mgp for many years.

My 4X4 is not fully broken in yet and I get 16-19MPG empty and 10-12MPG towing my 12K 5er. If you need a 4X4 I don't think MPG is a big issue. Other upkeep costs like Transfer Case lubricant changes are more a concern I would think. But thats just me.

bailer6334 said:

My 4X4 is not fully broken in yet and I get 16-19MPG empty and 10-12MPG towing my 12K 5er. If you need a 4X4 I don't think MPG is a big issue. Other upkeep costs like Transfer Case lubricant changes are more a concern I would think. But thats just me.

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Agree with all.  baller6334 - your specs sound spot on for our F350 and SRX, we get maybe a bit less towing in the hills.

I use my truck as a TV as well as to take it when I go hunting.  4 wheel drive comes in handle more in the off road rides to hunting spots but I've also had 2 times where I was glad I had it when towing.  The first time I was at my father in laws where I had it stored at his ranch in a field....well I went to pick it up and it had been raining on and off that day so the field was very wet.  No problems driving around the field but the way it was parked I had to go up hill after...as I was pulling out I could feel my truck slipping so I stopped put it in 4WD and it never looked back.  I would think for those guys that have diesels 4WD would be even more important since they are so heavy and tend to get stuck pretty easy.

I think a 4x2 will have a slight advantage in MPGs over a 4X4 but it is so hard to tell because driving habits and vehicle set-up play a way bigger roll in how well your vehicle will do.

For many years there was a company that made Locking Hubs for the front axle on Jeeps, these could be "unlocked' effectively turning the jeep into a 4x2.  The pitch was better gas millage (Since you are not turning the gears in the front differential).

Thus, I agree a 4x2, not only having less drag but also being lighter, will have better MPG.

But as I said, many folks think the 4x4 has more power or rather more towing power.

Is this true? I doubt it but I've never researched.

Towing capacity is figured by subtracting the truck's weight from the Gross Combined Weight Rating.  Carrying around several hundred pounds of 4WD components subtracts a like amount from how much you can tow without exceeding the GCWR, so 4WD trucks usually have a lower tow rating than the 2WD version.

The only 4x4s I know of that do NOT have freewheeling front hubs are the fulltime 4WD (or AWD) models.  Sometimes you have to get out and manually disengage the hubs when you're using 2WD, others disengage by driving a short distance in reverse.

If the front hubs are disengaged, the only real difference between 2WD and 4WD is the several hundred pound increase in vehicle weight caused by carrying around the 4x4 gear, a slightly higher ride height for the 4WD version and a slight increase in drivetrain drag caused by passing the power through the transfer case gears while in 2WD.

I doubt the transfer case drag has a measurable effect on MPG in 2WD mode, so if there is a difference in mileage between a 2WD and 4WD in 2 wheel mode, it's likely caused by something else.  Either carrying around the extra weight of the 4WD components or maybe the 4WD has wider tires or a more aggressive tread pattern with more rolling resistance than the tires on the 2WD model.

I've been towing with a 4x4 since the early 1990's and never used 4x4 while pulling a travel trailer.  If its icy or snowy, I feel I have no need to be on the road and wait it out.  I've only used it when unhooked from that type of trailer.  I would not spend the extra $ to buy and operate a 4x4 if I don't have a firm use for it.  It'll cost an extra couple grand to buy and will get at least 1 mph less than the same vehicle with 4x2.

I've used mine quite a bit pulling farm equipment trailers and also when traveling the back roads in the mountains.  When I buy my next truck, I'll get it again.

If you live and camp in Texas you might never need 4x4 with your trailer.  I need it from time to time to get in and out of campsites.  With the weather and the soil here you can get stuck in a flat, grassy meadow from the trailer tires sinking into the dirt a little combined with a loss of traction from the dew.

I have driven in Minnesota, on and off road, snow and mud, for decades.  4wd doesn't solve everything, and there are kooks who drive like crazy on snow and ice with it not realizing that it hasn't solved the handling and braking side of the problem for them.  Nothing worse though than a empty RWD pickup or van in icy weather.  You can get stuck on an icy hill on a city street with those.

Any 4x4 will have slightly worse fuel economy because of the extra weight of the transfer case and front axle (or rear, in the case of a vehicle that is made in FWD and 4x4 variants), though sometimes it's only 0.5 MPG and doesn't show up on the window stickers.

And in many cases 4x4s don't handle as well as 4x2 equivalents because the front suspension is compromised.  Dodge RAM pickups in the late 90s and early 2000s famously used a solid front axle rather than independent front suspension, for example.

4wd adds to the maintenance cost, especially if you use it, and in particular if you work it hard off-road.  I've replaced CV boots on my pickup truck and have had to pull the transfer case out of my Suburban to repair a loose shift fork dowel, and I replace the transfer case and front axle fluid in both every two years. 

My daily driver is a RWD sports sedan but I wouldn't be without a 4x4 in the garage for really bad weather.  I can always sell it if I move to Texas.

Saw a 2 wheel drive Chevy 2500 stuck on a slight incline in wet grass trying to pull a trailor out of a field. Had no room to back up. 4X4 sure would have made his day go a little easier.

The Op was interested in the difference in MPG between a 4x4 and a 4x2. I have a Jeep Liberty 4x4 and get approximately .7 mpg less than my neighbors Liberty 4x2. Both are 2008's. Variables of course are driving habits and use. I love the 4x4 for a toad as it takes less than 5min to hook up. When my wife drove into a sand pit and didn't want to tell me, I was able to go to 4 wheel drive and pull right out after the wife buried it.  The OP didn't say why they were comparing nor what the intended use was.

Lou Schneider said:

The only 4x4s I know of that do NOT have freewheeling front hubs are the fulltime 4WD (or AWD) models.  Sometimes you have to get out and manually disengage the hubs when you're using 2WD, others disengage by driving a short distance in reverse.

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Nearly all recent part-time 4wd systems use a split axle disconnect instead of freewheeling hubs.  It's a splined clutch in one of the front half shafts, usually the right because there's more room.  When in 4x2 mode, there's a shift fork driven by a vacuum or electric actuator that disengages the clutch, so that the right side axle is disconnected from the differential output gear.  The left side axle remains connected, but just turns the relatively small and low-friction gearing in the spider, with the right side output shaft then turning in reverse while the front axle input shaft remains stationary or maybe turns slowly from friction.

This is how my 'burb is set up.  Since it has independent front suspension with CV joints, the disconnect is placed in the solid axle portion inboard of the CVs inboard CV.  My old 1996 dodge, which had a solid front axle, had the same setup only no CV joint except the one in the steering knuckle.

If the front hubs are disengaged, the only real difference between 2WD and 4WD is the several hundred pound increase in vehicle weight caused by carrying around the 4x4 gear, a slightly higher ride height for the 4WD version and a slight increase in drivetrain drag caused by passing the power through the transfer case gears while in 2WD.

I doubt the transfer case drag has a measurable effect on MPG in 2WD mode, so if there is a difference in mileage between a 2WD and 4WD in 2 wheel mode, it's likely caused by something else.  Either carrying around the extra weight of the 4WD components or maybe the 4WD has wider tires or a more aggressive tread pattern with more rolling resistance than the tires on the 2WD model.

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While a front axle disconnect still leaves more components turning, it eliminates the larger losses from the ring and pinion and the more rapidly turning driveshaft between the transfer case and the front axle.

In any event, most of the MPG loss is due to the added weight, not to the added frictional losses.  It's typically a 5% difference, several hundred gallons of fuel over the service life of the truck, at a cost that is ordinarily lower than the purchase price of the upgrade from 2wd to 4wd on a new truck.

Good info Jammer. Thanks

On Jeep Wranglers, which many of us use, the disconnect is made in the transfer case, so even in two-wheel drive, the front dif gears, and front drive shaft are still turning.

Water Dog said:

On Jeep Wranglers, which many of us use, the disconnect is made in the transfer case, so even in two-wheel drive, the front dif gears, and front drive shaft are still turning.

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My 04 wasn't......Mine was a Rubicon. Maybe they were different IDK.

warsw said:

My 04 wasn't......Mine was a Rubicon. Maybe they were different IDK.

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You are right, some have Command-Trac which uses a two piece axle in the right axle tube that are disconnected via a vacuum shift fork motor that is mounted on the axle tube.