I have a 2004 forester automatic. I understand that there is a clutch mechanism which regulates power between the front and rear wheels.
I am told that under typical driving conditions 90% of the power goes to the front wheels while the remaining 10% goes to the rear wheels. This would be essentially a front wheel drive car under usual conditions with 10% simply rotating the rear wheels.
I would expect that when driving on a straight level highway, as we have in central Illinois, that the center clutch mechanism does not have a lot to do. The car operates primarily as a FWD car.
Around town I would imagine that is as different matter with revising and cornering. I would think the center clutch would be pretty busy determining which wheel(s) need to rotate and provide torque to them and which ones need to coast.
In normal every day small town driving I would think that that FWD mode would be more than satisfactory. The clutching mechanism would not need to be needlessly transferring torque to different wheels for light driving conditions.
I see the real value of the AWD system when traction is important for all four wheels and that traction requirement differs for different wheels. At this point the center clutch and other systems to optimize the traction to various wheels as needed.
For me this situation occurs primarily in the winter under slippery snowy conditions.
My question then is there any advantage, during the summer months, or any harm in inserting the AWD fuse so to disable the center clutching mechanism and using the car as a FWD car when driving conditions make the AWD system unnecessary?