Remember the days when one would have to get out of his 4x4 and lock the front wheels before engaging the 4WD shifter in the cab? Well these days most 4WD vehicles' front hubs remain in the locked position so you can just engage the shifter, and in most cases just push a button to put it in 4WD.

So I was told recently that, because of this, these vehicles get poor fuel mileage in 2WD mode because the front wheels are constantly turning the mass of the front axles and gears within the transfer case, causing excess drag. Makes sense.

But my question is this:
If this is truth, then why don't I get better mileage when in 4WD mode? I mean, since the engine is now supplying power throughout the system, eliminating the excess drag, why is my fuel mileage even worse in 4WD? Is it because now, unknowingly, I am actually delivering more fuel to the system in order to overcome this drag? Someone please explain, in layman's terms.

Thanks.

I don't know why you would expect better mileage in 4 wheel drive because you haven't eliminated the load of the axles and gear which were present in the 2 wheel drive mode. In 2 wheel drive you supply power to 2 rear wheels plus two front idling mechanisms, in 4 wheel drive you supply power to 2 rear wheel + 2 front wheels + 2 front, now driving, wheels, axles, gears. No?

But in 4 wheel drive you have twice the number of traction points on the road to help overcome the vehicle's intertia, No?

quote:

Originally posted by Kendor:
But in 4 wheel drive you have twice the number of traction points on the road to help overcome the vehicle's intertia, No?

Hmm.On that basis, fitting wider tyres, thereby giving a larger 'footprint' on the road, would improve mileage, wouldn't it ? This is not something which European designers, whose fuel cost problems are vastly greater than yours, have done.They've done it to get better acceleration and grip on the performance versions but that's a question of using more fuel, more quickly, not less

Hardly anyone here has a 4WD ; we don't see the point in offroad capability; save that Audi, eccentrically, have long made a 4WD 'Quattro' saloon because they tried to
persuade people it had better road- holding.Audi were really designing for their rally drivers, to win races where they drive sideways through forests, and used the sporty image to sell the cars to everyone else.

The problem is that the extra gearing and drive chain adds weight and takes a lot of extra energy anyway (extra friction, more work).The car doesn't go any faster (except in forests) and the fuel consumption is higher than that of a 2WD.