The price of oil is manipulated by a small elite of businessmen, politicians and bankers. Remember "Peak Oil" a few years ago when the price rocketed for no apparent reason ? Now we're in a glut.
The price of oil is dictated by the market and at the moment it is being flooded with oil by certain OPEC countries. So yes, it is being manipulated but at the supply side, not the price side as you maintain.
The reason there is a glut is that OPEC wants to keep the price of oil below the cost of oil that is produced from shale oil and from fracking. OPEC have been able to do this because new drilling techniques have enabled previously unrecoverable oil to be recovered. Further, oil consumption by the West has declined.
The Middle East wants to keep the US and Europe dependent on its oil. To do that it has to make its oil cheaper than that which can be produced from domestic sources and as shale oil and fracking supplies were becoming competitive the decision was made to flood the market and drive the price down.
An interesting side note to this is the damage that it is going to do to the Russian economy which really is a one-trick pony. What Russia is going to do about that is very uncertain given Putin's recent record. What it will do to the AVGAS price is very little I suspect. The finished product is imported into Australia in such small quantities that the oil companies would love to get rid of but its highly profitable and for that reason alone I can't see the price reflecting the fall in crude oil prices.