One time, when playing the board game, I was tempted to build it, but it's a huge gamble. If you manage to avoid a 1941 Barbarossa, I believe it would help : 9 BP lost in 1939 versus 1 extra resource from N/D 1940 to, say, M/A 42, so 7 turns with a 0.5 production multiple and 2 turns with a 1 production multiple (0.75 + 0.25 for the cities), 5.5 build points plus the later benefit of the extra oil.
On the other hand, those "lost" BP would hinder the USSR during a 1941 Barbarossa.
If playing the board game with the extra buildable Oil in Siberia, they are cheaper : 7 PB and 4 turns for the oil in Omsk of Novosibirsk, so the Synth Oil is probably not a good idea.
The other players on my team considered it a bad decision, so I think I did not build it after all.