There was slightly more oil available from Sakhalin/Karafuto using 1940 technology than has been mentioned. The figures given so far are from the Japanese concession and are not too different from an unsourced estimate from Wikipedia of 1,000,000 barrels per year or about 140,000 tons. However,
http://www.sturmvogel.orbat.com/SovOil.html gives 588,000 tons for the Soviet output for 1940 rising to 1,200,000 tons by 1945. Thus we can guess that Japan might produce a similar output, perhaps slightly earlier because it would have been the major Japanese source of oil.
What were Japan's minimum requirements?
http://www1.american.edu/ted/ice/japan-oil.htm#table gives 3,680,000 tons of imports in 1935 rising to around 5,000,000 in 1940 (presumably due to the war in China and a larger fleet) referencing B.R. Mitchell "International Historical Statistics 1750-1993" and Walter J. Levy "Oil Strategy and Politics, 1941-1981".
Thus Sakhalin could have produced approximately a third of Japan's peace time requirement and around 20% of the 1940 requirement or as Bill notes around 2-4 months of the WW2 fleet requirement. Clearly that is not going to have a huge effect by itself. It may slightly reduce the urgency of the Japanese negotiations, especially if the extra output has allowed larger stockpiles to be assembled. Clearly if Japan has time (two or three months) to reflect on Germany's failure to take Moscow, they may try harder to reach a negotiated settlement. However, there probably wasn't a deal available unless something happens. The luckiest something for Japan would be an incident starting a Germany - USA war. Then the USA would really prefer Japan to not pin down a significant fraction of the Anglo-American forces and might end the embargo in return for a ceasefire in China with an agreement to withdraw over three years (Manchuria included/excluded?) on the calculation that in three years time they will have won WW2 and can tell Japan exactly what to do. However, after WW2 perhaps they will need allies against the USSR.
The butterflies of the 1905 POD will spread rather wider. Firstly, Japan will have four times as much oil production. The extra oil men are more likely to find more oil, for example in Manchuria. Secondly, Japan will be just a little richer with unclear effects. Thirdly, without wanting to seize Sakhalin, perhaps Japan is less interested in a Siberian intervention? If the Siberian intervention were mostly an Anglo-American operation, Japan's relations with the USSR might be different. If Japanese troops were needed, perhaps political deals involving China might be made?
And finally, if Japan received Sakhalin in the Portsmouth Treaty, Japan's relations with the USA would almost certainly have been better! They may deteriorate but it is also possible that Japan would have welcomed more US investment and that US companies would have exerted influence to keep business running smoothly.