Building commodity tracking ETFs can be difficult. People argue that such ETFs build on stocks like the CRBQ from Alps/Jefferies are not a commodity pure play. On the other hand ETF build upon futures has leakage at each roll-over during contango.
Below is a graph of different ETF and ETNs build to track Crude Oil. What I did was to index the evolution of the individual ETFs and WTI crude since 02.01.2009. You will see that the DBO seem to do a better job at tracking WTI than the more well-known USO or USL. (The ETN OLO is on par with DBO but has a higher expense ratio and ETNs has counterparty risk.) I will be interesting to see if this will reverse during backwardation.
Expense Ratio:
DBO 0.5%
OLO 0.75%
USO 0.45%
USL 0.60%

Disclosure: Long DBO