what is the best four wheel drive or all wheel drive vehicle with the best gas mileage?

I'd go with a late model Subaru Legacy or Outback, with the 2.5 liter 4-cylinder engine. It's a little bit larger than the WRX and would provide more passenger comfort. They have adequate performance, AWD is standard on all Subarus and you should get about 26-30 MPG on the highway

They are all the same, some might have more sophisticated controls than others and save you a little but in the end you need to remember the following rules about AWD vehicles.

1.) two units that transfer energy to the wheels

2.) all the wheels are limited by the type of unit

3.) any changes done anywhere in the vehicle will make the same changes in the opposite section of the vehicle

4.) for every benefit there is a deficiency somewhere else

Basically if an AWD vehicle saves you fuel it will cost you much more somewhere else, maybe wheels, fluids, steering. Simply because in the end is power to weight that determines the efficiency, is not necessarily the lightest vehicle that would give you the best mileage is the one that has the best means to transfer the power, and in all AWD vehicles is an optimum North American setting that would be idiotic not to implement depending on where the vehicle is sold. If you are racing that is a different story you will get a variety of AWD settings that are unique to the vehicle it self but not fuel efficient at all. hope that answers your question, in the end it would come down to looks for me, and cost.

Having the four wheel tension as an determination and not ideal that is going to nonetheless shrink the mpg of the motor vehicle by way of greater weight of the kit for the four wheel tension ( like a heavier front axle, differential, and so forth )

pick up a copy of Consumer Reports, they will give you the best evaluation of any vehicle that interests you.

I assume that you expense the mileage for hauling clients around, so would you consider two cars? one to commute with and another bigger/prettier one to keep at the office. Since you would use it only for hauling clients around it could be 100% expense deductions.

then if for some reason you leave the job your employer would keep and pay off the rest of the vehicle since they'd already have been paying for it anyway.

maybe a Subaru wrx