All are fine if you can accept that their daily answer is accurate to no better  than +/-3% and therefore use long averages (minimum a month).  If you are sensitive to the last 10 cts out of $20 on a Brent settle or 1/2%, then you need to grow some balls and sell flat price and quite blaming other people for your situation.  The Scandi's I traded with understood this completely and were just as quick to play the same games while their management bleated like sheep.  No tears from me for Statoil.  

Same for the Mid East lot.  They all want a constant high price off of a formula that absolves them of responsibility.  Which is why I think your IOB will never fly.  They don't really want control because with control comes responsibility and accountability.  They want someone else to set the last few % and still have the lean always go their way.  ho ho ho.

As for GSCI, all I saw from the other perspective was a huge futures position, with rigid rollover rules such that any nimble local or player could front run it to death.  The GS trading desk was struggling to find ways to keep those settles from being consistently shaded against the index investor.  But again, investing in  an index with a structural flaw like GSCI is your own mistake.  I note that now that we've had nearly 2 years of deep contango such that each months rollover is killing the index, GS is selling it off.  Hard to flog an index that returns -20% when the market is flat over a year.

I never saw any overt collusion though I have had it proposed to me by a large Dutch trading house player. Rumors abounded but I never saw hard evidence or witnessed anything with my own eyes/ears. BP were very, very aggressive about pushing around the market.  No surprise that they are getting bad press for their LPG and other books in the US.  I will not be surprised if they are found guilty.  If Europe had any real regulation, many would have gotten in trouble there as well.  Half of ENEL would have been in jail and all of their suppliers prior to about 1992.  I see some Germans are about to get convicted for bribes to ENEL managers in recent times on procurement.  Some things don't change I guess.