With the creation of this mega thread specifically dedicated to Oil, I've decided to copy my post from the supply DD:
The more I think about the lifetime fuel cost of a unit being included in the initial production, the less I like the idea. Take for example two nations constructing tanks. The first nation is engaged in high tempo active operations close to its own borders against an enemy equipped with plentiful high quality AT weapons. The tanks get constructed, loaded onto a train and unloaded a few miles from the front line. Then they drive to the front and engage the enemy, being knocked out within a few days. They only fill their petrol tanks once in their lifetime. The other nation is engaged in low density operations against an enemy who is behind in technology and lacking in good AT weapons. Those tanks could drive thousands of miles before suffering a catastrophic failure requiring the tank be written off. Spare tracks, replacement parts and servicing the engine keep it going without the need to have anything like a total rebuild, and even where rebuilds are necessary the armoured plates and basic frame of the tank are still fine. Those tanks could fill their petrol tanks say 50 times over the course of their lives. These example may represent the extremes, but if its averaged out, the first nation has to expend 25 times as much oil in production than its tanks would actually use while the second is able to drive twice as far as its fuel supplies should allow. Its a deeply flawed theory.
I can understand not wanting to have stockpiles. but I think there is a better way of handling fuel in HOI4 than has been illustrated so far. This would be to limit operations based on the proportion of fuel supplies to units that need fuel. For example lets say that 1 point of Oil allows 10 armoured or motorised battalions or 500 planes or 10 destroyers to operate without restriction. Each day the amount of oil is compared to the units/planes/ships that need it giving a proportion, lets call it 80% for this example.
For ground units it could simply be a matter of reducing the base movement of fuel dependent units where there is a shortage. So instead of moving at say 10kmh, the 80% fuel supply would limit movement to 8kmh.
For aircraft, the limitation could keep planes from flying, so at 80% only 80% of planes at each base could operate that day.
For ships, I'd say that each hour spent in port allows them to spend say 10 hours assigned to a mission, to a maximum of 1000 hours before they have to return to port. With fuel supplies at only 80%, each hour in port would only allow 8 hours on mission, thus keeping them in port longer than would otherwise be the case. It should also be possible to mothball ships so that they can't move but don't count against the fuel requirements.
With a system like this, a nation with fuel shortages would have an incentive to reduce the number of fuel dependent divisions to improve the efficiency of the others, which the Germans did when they converted 2 motorised divisions back to infantry in 42/43. A nation with significant numbers of obsolete aircraft would have an incentive to keep them in reserve so that the operations of its modern aircraft were not impacted, modelling the retirement of older models that all major nations did, whereas the current system will have those old planes keep flying until they're all destroyed. The navy of a nation suffering from fuel shortages would spend more time in port than its opponents, better reflecting the problems besetting the Japanese and Italian navies.
