The sagging US$ makes this a bit misleading in some ways - it would be nice if oil prices were expressed against a basket of currencies, instead of one that is under huge pressure from all directions.

Well, taking the "Freezing Point" approach, it doesn't matter if the oil price rises or the currency drops or the economy enters a recession with negative growth or there's overall inflation of - the key thing is that fuel affordability drops for that country.

The people could afford so much fuel, and now they can afford less. The wasteful industrial society comes under strain.

RE sagging US $
There is some analysis that has the $ leveling out and perhaps even rising a bit. At this point, it is beginning to make sense to think of almost all the dollar-index currencies as being under downward pressure. If the $ sinks more it is only because the Euro is not sinking as fast. A real race to the bottom. If the remnimbi was in the dollar-index basket, it would probably be rising for real.