Investor’s Daily had an interesting article about the performance discrepancy of oil ETFs. In a previous post, I alluded to the fact that some segmented ETFs can easily stray from their stated benchmark, and that you can’t always be sure what you’re buying.
It appears that this happened to 2 oil ETFs, namely OIH and USO. You would think that if the price of oil goes up, so would any ETF tracking that sector. Apparently, that’s not a guarantee. Look at the chart below: 
If you had bought OIH back in October 06, you’d been riding an uptrend and made some profits. If you had picked USO, you’d be down with your investment.
It has to do with which spot price is used as a benchmark and if it is reached by a certain date (on the futures market).
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How can you track this to be sure the ETF you selected goes in lockstep with the price of oil? Check the closing price of oil on any given day; if it’s up and your ETF is down, you better monitor it very closely to be sure it was not just a one-day aberration.