Warning: Long post...
I don't know about you, but the rapid drop in Pacwar Japanese Oil reserves has always driven me crazy. I understand the reality during the war that Japan did gradually run out of oil as the war progressed, but it's always bothered me that I couldn't understand the mechanics of the oil reserve loss in the game. It always seemed to drop much faster than I thought it should based on the fuel I was using versus the oil I was able to bring in from the Dutch East Indies...
So, I spent some time trying to figure out the mechanics, and I think I've uncovered a major issue in the way routine convoys actually work in the game. Let me try to explain.
First of all, we all know about the weekly consumption of oil taken from Japanese heavy industry. In the current Pacwar version 3.2, that amounts to about 60 X 25, or 1500 units of oil consumed per week.
To counteract this loss, we have the routine convoy system picking up oil from the Dutch East Indies and other bases. I won't go into the details on that major subject here, but note that it is very important that you keep as many TK's in the Japanese home islands to maximize the collection of oil for your reserves. Sounds OK so far...
Here's the first major issue. Every bit of fuel provided to Japanese bases during the routine convoy phase is taken directly from the Japanese oil reserves; it is not taken from fuel stockpiled in Japanese home island bases. I never realized this before. I had always thought that's what all the large fuel stockpiles in the home islands were for. Fuel at these bases actually only gets used up if you create manual cargo TF's to ship it out.
OK, how much fuel does the routine convoy system actually send to your bases? The amount consumed by air groups and TF's is actually not that significant (another subject I'll save for another time), the big culprit here is the amount of on-hand fuel that your HQ's demand. Here's how it works.
Each of your HQ's located at a port demand fuel on-hand equal to about 2000 X Port Size. So for an HQ base with a port size of 9, your HQ will want on-hand about 18000 units of fuel. This is not consumed every week, it is just the amount that your HQ wants on-hand for potential operations. If your HQ base has less than this amount, then the routine convoy system will attempt to bring in fuel (taken from your oil reserve at an equivalence of oil X 4 = fuel provided) to meet your HQ needs. The routine convoy system will actually attempt to bring in fuel equal to 2 times the difference between the amount desired and the amount actually on hand. So if your HQ base with a port size of 9 only has 8000 units of fuel on hand, then the routine convoy system will try to bring in (18000 - 8000) x 2 = 20000 units of fuel (I know, sorry for all the math ). This will reduce your oil reserves by 5000!! You think that sounds bad? Well it gets worse (and this is where I think the real problem exists).
The routine convoy system provides fuel as follows: As mentioned before, for example, let's suppose we have an HQ base that wants 20000 units of fuel ((18000 - 8000) x 2). So, first, subtract "5000" from our oil reserves. Now, do we have enough MCS cargo ships in Japan that can supply 20000 units of fuel via mixed supply??? Oh gee, no we don't... Oh well, suppose we only have enough cargo ships to supply 3000 units of fuel. Well, that's all your HQ base will get! But the 5000 in oil reserves is still gone!!! And, by the way, your routine convoy system will try again next week to meet your HQ's unmet on-hand fuel demands. You know what this leads to...
So, how do we protect our precious oil reserves from this potential disaster?
1) First of all, be very careful where you place your HQs. Try to build up fuel supplies manually at a new base before moving your HQ there.
2) Other bases connected by land routes to your HQ base will continually draw fuel away from your HQ base (Shanghai is notorious for this). So fuel supply will be easier to handle at bases without significant land route connections.
3) Placing HQ's in Japan home island bases or on a base without a port will eliminate the routine convoy issue.
4) Placing your naval HQ's in a TF will eliminate the routine convoy issue.
5) Setting up manual cargo TFs (with MCS providing mixed supply) can keep your key HQ bases supplied with the fuel levels they demand.
6) If you have 2 HQs at the same base, the on-hand fuel demand will double! Watch out for this if you unload an HQ from a TF onto a base already holding another HQ.
If you do these things I think you'll see a significant improvement in your oil reserve maintenance. May your oil reserves live long and prosper...
By the way, the same rules apply for HQ base supplies and resource consumption (at a rate of resources X 10 = supplies). It's just not as big an issue in the current version of Pacwar due to the large number of resources provided, and if you're careful with the fuel / oil maintenance issue, it'll automatically take care of any resource reserve issues.