fueleconomydotguv confusion

[spaceman]

ok so when you go to fuel economy .gov and type in make/model.
does the fuelecon crtieria for 4x4s assume constant 4x4 operation for mileage estimates?

 

[thomsbrain]

almost certainly not unless the vehicle has full-time AWD. But there will still be a mileage penalty due to the added weight.

 

[Jumpem]

I would assume all of the EPA estimates for 4WD vehicles are done using 2WD (unless it is full-time 4WD/AWD).

 

[Throckmorton]

It doesn't matter unless you have unlocking hubs. All the same hardware turns in 2WD mode, except it's the road driving it all through the front wheels

 

[spaceman]

does anyone have a solid answer on as to how they arrive at those numbers?
ex=f150 4.6l 2wd vs. 4.6l 4wd

 

[iamwiz82]

Originally posted by: spaceman
does anyone have a solid answer on as to how they arrive at those numbers?
ex=f150 4.6l 2wd vs. 4.6l 4wd

It was my understanding that if the vehicle had the option for 2wd then the tests were run while it was in 2wd only. Otherwise those with 4Lo would have pathetically low numbers.

 

[Nyati13]

The EPA estimates are performed on a road course. There is no off-road segment for 4WD vehicles. It is 2WD for all vehicles that can, and AWD/4WD-Hi for all-time 4WDs. There isn't any confusion about that.

 

[Throckmorton]

I'm trying to tell you, it doesn't matter whether the vehicle is in 2wd or 4wd mode.

The driveline hardware turning is exactly the same.

 

[spaceman]

Originally posted by: Throckmorton
I'm trying to tell you, it doesn't matter whether the vehicle is in 2wd or 4wd mode.

The driveline hardware turning is exactly the same.

so what you are saying is i get the same mileage in my tacoma in 4x4 hi as i do in 2wd mode?
sure doesnt seem like it at the pump

 

[Jumpem]

The answer has been given several times. The EPA tests are done in 2WD.

Yes, your mileage will be lower in 4WD, but they don't account for that.

 

[iamwiz82]

Originally posted by: spaceman

Originally posted by: Throckmorton
I'm trying to tell you, it doesn't matter whether the vehicle is in 2wd or 4wd mode.

The driveline hardware turning is exactly the same.

so what you are saying is i get the same mileage in my tacoma in 4x4 hi as i do in 2wd mode?
sure doesnt seem like it at the pump

No, but you shouldn't be driving around in 4wd if you have a 2wd option and the weather is fine. Fine being 97% of the time.

 

[Bignate603]

Originally posted by: spaceman

Originally posted by: Throckmorton
I'm trying to tell you, it doesn't matter whether the vehicle is in 2wd or 4wd mode.

The driveline hardware turning is exactly the same.

so what you are saying is i get the same mileage in my tacoma in 4x4 hi as i do in 2wd mode?
sure doesnt seem like it at the pump

If you don't have a center differential I really don't suggest driving in 4wd all the time.

Throckmorton is right, unless you have unlocking hubs to completely disconnect front drive line (or the vacuum disconnects which never seem to work right after a few years) you'll still have a noticeable penalty shifted into 2wd. Without a center differential in 4wd on pavement I think you'll get even worse mileage because the front wheels and back wheels will fight each other a bit if the wheels aren't completely straight. However, considering the stress you're putting on your driveline without that center differential in 4wd the extra gas is the least of your worries.

 

[LTC8K6]

Using 4-wheel drive reduces fuel economy. Four-wheel drive vehicles are tested in 2-wheel drive. Engaging all four wheels makes the engine work harder and increases crankcase losses.

As the site says, tests are in 2 wheel drive.

http://www.fueleconomy.gov/feg/factors.shtml

 

[Zenmervolt]

Originally posted by: Throckmorton
I'm trying to tell you, it doesn't matter whether the vehicle is in 2wd or 4wd mode.

The driveline hardware turning is exactly the same.

New 4WD trucks use electronic locking hubs which are indeed disconnected in 2WD mode. It's only full-time AWD/full-time 4WD systems that will fit what you describe.

ZV