One can come up with a time line thats somewhat plausable where Stalingrad falls.
Take one of the better Luftwaffe General Wever lives scenerios. JU88 produced as a level bomber earlier, No ME210, a limited run of DO19 prototypes as FW200 replacements etc..
What you have is by late 41, early 42 a Luftwaffe that because of these PODs has an increase in reserves is able to keep up its strength through the attritional fighting, a more effective Luftwaffe in the Typhoon and Soviet counter attack stages of 41, with these butterflies the Germans avoid the Demanysk airlift so the Luftwaffe suffers further less losses.
So June 1942 arrives and you have a German offensive supported by much a larger Luftwaffe, with incremental increases in ground forces from having more Luftwaffe support over the fall and winter 41. Stalingrad is taken on the rush in early August 1942.
German drive in the Caucasus is reinforced and the Germans are able to take Grozny and cut the railway south from Asktrahan. Maybe the German could find a way over the mountains and get through to Tupase or Sochi or someplace further down on the Black Sea.
Its an awful long way to Baku though (most Soviet oil came from Baku), lots of difficult terrain, supply difficulties are immense, better air supply can help in some places, but the Soviets are also not tied down at Stalingrad, can use the Caspian as a supply route, had some intrinsic supply capability in the Caucasus as well as access to Allied Lend Lease from Persia.
Likely the intevitable Soviet counter attack comes just the same as OTL, the Germans don't have to have everything in Stalingrad and so don't suffer the complete OTL disaster, the Soviets can pick on the their Allies just the same, so the German have to pull back to the 1942 start lie eventually just the same as OTL (with less losses OTL).
Any German victory POD needs a collapse of the Soviet state/ system. There were times that was close perhaps, October 41, July 42, maybe a little better German performance at these critical times makes the Soviet system dysfunctional enough due to low morale, famine on the home front, other shortages, people not obeying orders, Stalin shot by more created enemies, etc... Things breaking down enough that a negotiated 1918 style peace with Germany is possible.
Without that its hard to see a German victory against the intevitable Soviet preponderance in resources+Lend Lease.