Valero (NYSE:VLO) was the first big refiner to report earnings, doing so earlier this week. In this video, contributor Aimee Duffy takes a closer look at the company's gross margin per barrel for its mid-continent operations, which shrank 18% year over year. Aimee discusses how Valero's past numbers have compared to the other big mid-con refiners, and if there is even a point for investors to make the comparison at all.

Fool contributor Aimee Duffy has no position in any stocks mentioned. The Motley Fool owns shares of Western Refining. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.