Query re: mileage difference between 2WD and 4A

[Jedburgh]

First off, I am grateful for this forum, and thank the folks who invest their time running it.

Quick preamble: I spent 25 years with AWD cars. Hadn't even touched a RWD vehicle in those years. Got the Raptor, a 2020 SCAB, and thinking of mileage, have mostly been running it in RWD. Well, come the day, some slick pavement and a lane change under power, and it went all Duke Boys on me, which of course I should have damn well expected. Anyway, reeled it in, but have been running 4A on any day where the pavement isn't bone dry since.

The question: if you aren't triggering the second set of drivewheels, does leaving it in 4A have any effect on the mileage, and if it does, would you be so kind as to clue me in as to why?

Thanks, Jeds.

 

[gopher870]

I don't know the answer and find it to be an interesting question. I have used 4A with the screen that shows where the power is being distributed on acceleration. I tried different variations to see how much power was being split between front and back. I was never able to accelerate without the front wheels not engaging at all. No particular reason, just ******** around in my Raptor! What....you don't do that?! Anyways, I imagine there would be some hit to MPG in 4A as it appears even under gentle acceleration the front driveline is doing some work.

 

[PlainJane]

The mileage difference is not enough to worry about, your right foot has more effect on your mileage. 4WD is a different story.

On the freeway I can get 20 mpg if I keep it at the speed limit.

 

[df4801]

First off, I am grateful for this forum, and thank the folks who invest their time running it.

Quick preamble: I spent 25 years with AWD cars. Hadn't even touched a RWD vehicle in those years. Got the Raptor, a 2020 SCAB, and thinking of mileage, have mostly been running it in RWD. Well, come the day, some slick pavement and a lane change under power, and it went all Duke Boys on me, which of course I should have damn well expected. Anyway, reeled it in, but have been running 4A on any day where the pavement isn't bone dry since.

The question: if you aren't triggering the second set of drivewheels, does leaving it in 4A have any effect on the mileage, and if it does, would you be so kind as to clue me in as to why?

Thanks, Jeds.

Yes. pretty sure mileage takes a hit in 4A as it will send some power to the front as well, even on dry surfaces. someone smarter than me will have to explain why.

 

[FordTechOne]

When you are in 2WD, the front driveshaft, front differential, and front axle half shafts are not turning. With 4A or 4H engaged, all of those components are constantly engaged, regardless of whether torque is being transferred through them or not. The extra drag from those components is what reduces fuel economy.

 

[04Ram2500Hemi]

I’ve honestly never thought about it, but I’m guessing you’d lose some fuel economy. The real question is how much is it to repair a front fender if you bounce off a guard rail when you could have used 4A? I’ve seen a completely dry highway get spooky as shit when you hit the right bridge deck. When in doubt, throw it in 4A.

 

[Jedburgh]

Thanks to all, especially FordTechOne for the "why" of it. And absolutely agree with 04Ram2500Hemi.

 

[WyoRaptorrrrr]

I love this forum!! Where else can you get a bunch of guys messing with trucks and debating mechanical friction

 

[KAH 24]

First off, I am grateful for this forum, and thank the folks who invest their time running it.

Quick preamble: I spent 25 years with AWD cars. Hadn't even touched a RWD vehicle in those years. Got the Raptor, a 2020 SCAB, and thinking of mileage, have mostly been running it in RWD. Well, come the day, some slick pavement and a lane change under power, and it went all Duke Boys on me, which of course I should have damn well expected. Anyway, reeled it in, but have been running 4A on any day where the pavement isn't bone dry since.

The question: if you aren't triggering the second set of drivewheels, does leaving it in 4A have any effect on the mileage, and if it does, would you be so kind as to clue me in as to why?

Thanks, Jeds.

——-

@FordTechOne captured drivetrain friction losses.

Calibration setups/adjustability settings of AWD trends to be different different in cars vs. a top heavy/front weight biased pickups.

The calibrations for a front end biased truck with a light rear—will be different from a car where the calibration balance is more rear biased—and vectoring is biased to the rear (or adjustable).

Less frictional losses + better calibrations for better weight balanced AWD.

 

[isis]

I love this forum!! Where else can you get a bunch of guys messing with trucks and debating mechanical friction

Now you’ve called @Oldfart

he’s the resident mechanical friction expert