Yes there are some ways to improve the oil management, but it is still little unless you play sitzkrieg between France and Barbarossa.
Then yeah you can swim in oil. Reach your cap. And then probably have UK swamping the map with units.
For now at Poland, in T1, Germany can pratically waste their whole oil stock that they begin the game with.
Which is 100.
By Barbarossa their cap is 800-900 (I think that may be generous), let's assume they got it. But also how many more troops have they got, that require fuel, from the starting setup?
Thus how long such oil will last?
2 strikes of a Medium Bomber is -6- oil. (And in many cases they net 0-1 damage).
An armour attacking 3 times consumers -6- oil.
Assuming Germany has let's say 10 planes (think that's low), averaging 2 oil each (1 fighters, 2 cas, 3 medium), 2 missions each = 40 oil a turn
Now let's add Panzers / Mechanized. Let's say that Germany has 10 of them as well. And that each move, and attack 3 times (spending 8 each) = 80 oil a turn
That is barring Mediterranean / Atlantic anything else operation.
It is litterally needed to play sitzkrieg for 4 turns of offensive, then sitzkrieg for almost year, 4 turns offensive.
If an issue is not seen in that, I do not know what to say.