Redirecting Japanese submarines toward fleet tankers

What if Japanese submarines had been assigned to attack enemy fleet tankers?

The effect could have been large, although the brief exchange does not quantify the counterfactual.

The prompt shifts Japanese submarines away from seeking major warships and toward enemy fleet tankers. Such a change could have had a large effect because it attacks the support behind fleet operations rather than only the combatants. The answer is deliberately brief and does not quantify how many tankers could be found or sunk. Earlier discussions of Kantai Kessen provide context, while Japanese submarine and carrier doctrine merit fuller treatment elsewhere.