Try The Pearl Harbor Papers: Inside the Japanese Plans by Donald Goldstein and Katherine Dillon (1999) as an easy to find source
Quoting from there:
Akagi had 300 tons of drummed oil overloaded aboard
2nd Carrier Division (Hiryu, Soryu): 100 tons of drummed oil, 200 tons of canned oil overloaded
Cruiser Division 8 (Chikuma, Tone): 100 tons of drummed oil, 480 tons in trim tanks and waterproof compartments overloaded (emphasis mine)
Yes, they were at the ragged edge of their fuel envelope. OTOH, the nominal capacity of one extra oiler would be 8,000-10,000 tons of fuel oil. Yes, the IJN was starved for fleet oilers (the USN didn't even really have enough until late in the war), and scraping up eight (I earlier implied seven, sorry) for the OTL attack just barely got them there and back, as the decision to carry drums of oil illustrates quite vividly. Still, they had about 20 AO in the fleet at the time. One more is tough, but not ASB.
My notes have the non-destroyer elements of the task force with a combined bunkerage of about 47,000 tons. Eight DD would add about 5,000 tons more (don't have the class of each DD in the raid handy), and the oilers themselves have about 2,000 tones each (again, I don't have data by class). Nominal radius of everything except the DD is at least 7,000nm at no less than 16kts, though of course
much less at high speed. IIRC the Midway attack force (the 12/41 one, not the 6/42 one) had another DD division which also used the Pearl Harbor oilers to refuel, so add another few thousand tons of tanks that need to be filled.
And to repeat again: the OP made no claims about the Japanese winning the war, and I didn't mean to imply any such thing either. I'm curious about the effects the OP POD would have had on the course of the war. The outcome is certain; Japan is going to lose, and quite thoroughly (possibly even, as I tried to make clear, FASTER than they lost OTL). HOW they lose can still be of interest, IMO. If it isn't interesting to you, that's fine.
I thank all those, especially CalBear, who have posted substantive information.