Hitler is dumb leader. why would he drive to the caucasus. He knew that the supply line would get overstretched. And he never needed to go to Stalingrad to cut he Volga river. And even if he did get the oil fields in Baku or the southern caucasus, delivering that oil to the wehrmacht would've been a disaster. You have to keep in mind that the overstretched supply line. the Vast distances in the Soviet Union, and Germany running out of oil. Operation "BLAU" would've never succeeded.