On my Jeep SUV, I normally drive with rear wheels only engaged; when there is ice or snow, I engage all 4 wheels, which means lower gas mileage.

AWD means that all four wheels are engaged at all times, but some claims in the papers point to some kind of 4X4- read adds carefully.

Lexus (my son has one) and Cadillac both offer AWD; a monitoring system automatically distributes the power delivered to each set of wheels depending on conditions. The Lexus is highly engineered; I don't know about others.

The Suzuki AWD on the SX4 powers the front wheels, and delivers power to the rear wheels when necessary. I have friends who like it, they are skiers.

In other words, not all AWD are the same.

I am familiar with 4X4 pickups- helped out on slippery slopes and ice more than once- but don't know anything about AWD pickups.