The new map is an uneasy compromise, with some tts values reflecting oil wealth, others not.
Personally I prefer adding industrial base and mineral resources together to create a single economic index, but the separate oil values have been tried:
http://www.basesproduced.com/aaa.html
The big problem is that the Allies always have more than enough oil, the Axis hardly ever enough. Forcing the Axis to take oil centres to keep going makes their moves very predictable.