I'm sure some of the problem is due to the weaker dollar, but probably more is due to the system of manipulation and speculation that really sets the price here.
Nobody really manipulates the price of oil. It is bought at auction much like this shorty bus. The seller believes he can get more. He might get more or he might have to keep it. If a person feels they can buy it at auction and sell it for more at a later date, more power to them.
I believe our problem now, is that during the last run up, fuel prices never reached the point we collectively said too much. Bush released some of the government's stockpile to bring prices down before we decided to change our ways.
In February of this year, Detroit had a great sales month. Most of the vehicles sold were SUVs and full size pickups rather than the hybrids the government keeps hyping.
Lately, I've been reading that China and India's oil usage will have more to do with the price of diesel than our usage. We use far more per person but those countries have far more people.
Recently, India has been raising the price they will pay per barrel while China has been buying into supply with strategic partnerships around the world.
At this juncture we're lucky the dollar is still the currency of oil. It lowers the cost of our oil purchases. That only happened because of Pres. Obama's quick action. The Euro was briefly looked at as the currency of choice with the latest idea is a basket of currencies. This too helps us as there will be a lot of hemming an hawing over the basket's makeup.
For me personally, I bought my bus with a $7.00 per gallon target. I've had even more fun and saved more than I expected. I can't say I've saved actual dollars but that points more to items wearing out than the price of fuel.