TL;DR
The fluid damage modifier of the three oil types for the flamethrower turret should be in the FactoriopediaWhat ?
As the in the tl;dr I don't think in the Factoriopedia is any mention of the modifier the light and heavy oil gives to the flamethrower turret. It's only in the tooltip.Neither on the site of the turret, the ammo category or the fluids themselves. Personally I think it should at the fulids themselves, since the other ammo items havet their effects there too.