Explain why the 4x4 and 4x2 would not get the same mpg until you switch to 4x4?

exactly, wtf is this thread about again ?

for mpg

any gram of extra weight decreases mpg
any difference in tire psi or tire make/model
any difference in vehicle height
any added friction from cv's or propeller shafts
mud flaps, front air dam, spats, antenna type

all the above affects mpg

 

The biggest difference between a 4 wd not engaged and a 2 wd engaged, is the ride height. The increased drag from wind resistance is the single biggest factor. Yes the weight matters but the front differential actuator keeps the diffential drag from being a factor and the half shaft drag is minimal. The new Tacoma is higher this year and over all, this is one of the biggest problems always associated with Tacos in general. They are built for off road and have a natural disadvantage. The EPA numbers for two wheel drive will be better then 4 wd, but not as great as they used to be be because all 2 wd trucks are essentially pre runners. I would suspect that the wind screens on front help some what but they aren't miracle workers. This is why there was so much work on fuel economy for the little gain of 10%. Off road Vehicle mpg gain comes grudgingly and in older Tacos especially, any thing you do to increase ride height increases drag.

 

I haven't read anything in this thread. But here is why:

Highway. There is no listed difference in highway fuel mileage.
Street. You have to accelerate more mass, F=ma. You have to cause more angular acceleration of the front drive line, half shafts, and spindles, T=Ia

 

Added weight of the transfer case, front differential, front prop shaft, front drive shafts/axles.
Added driveline losses of having to go through the transfer case (even if it's not spinning the front prop shaft).
Added driveline losses of having to spin the front drive shafts/axles and differential internals (even if it's not spinning the front prop shaft because of A.D.D.).

Jeff

 

Years ago there was a significant difference. It is much less today. All things being equal a 4X4 weighs about 500 lbs more and will get less than 1 mpg less than a 4X2 truck. The problem is that things are not always equal. A street tire will weigh less and roll with less resistance than a mud tire. All terrain tires are a decent compromise. Most 4X4's also set up higher resulting in less aerodynamics, especially after winches, push bars slider's etc. are added.

Before gas went over $1/gal full time 4X4 trucks were just becoming the rage. These rigs were in 4X4 all the time with a locking system for off roading. I had a 1975 Jeep J-10 truck in the late 70's that was good for 6 mpg city and 10-11 hwy. The 4X2 trucks of that era were good for 10ish city, 15-16 hwy. That made a difference, today I'd not let the fuel mileage difference make the decision for me between 4X4 and 4X2.