This oil refiner is up 25% so far in 2009, but it is still way below the almost $30 per share it traded at a year ago. Now, just under $17, Tesoro (NYSE: TSO) trades for eight times forward earnings.

Given that oil prices are on the upswing, look for TSO to sell refined product at higher prices at the pump. Buy low; sell high. It is that simple for TSO.

As long as we avoid the massive swings in crude prices, this little oil refiner can expect to see its stock double in value over the next year or two.

I rate TSO a B or buy.

Up next: Oil Stock #2.

With oil prices heading to $70 or more, owning oil stocks is a must for any investor looking to generate maximum returns.

Crude traders are betting that a stronger economy will result in increased demand for oil. At the same time, OPEC is holding firm on production cuts that reduces supply.

And let's not forget about the summer driving season which officially kicks off this Memorial Day weekend.

All of these factors mean investors can confidently operate under the assumption that oil prices will go up in the foreseeable future.