I would compare any commodity ETF with the underlying before I assumed it correlated. I don't know how well USO is correlating now, but there were big problems in the past related to unusual contango in the crude market.
Basically, USO buys crude futures and rolls them over. If the far-dated months are trading well in excess of cost of carry, anyone pursuing a buy and roll strategy will take a haircut everytime they roll.
An alternative would be to buy an oily pure-play E&P company, but any stock is going to be affected by the overall market as well as crude prices.