The following video is from Thursday's Digging for Value in which host Alison Southwick and Motley Fool energy analysts Joel South and Taylor Muckerman dig into the most exciting stories in energy investing today.

In this segment as part of the Motley Fool's "Ask a Fool" series, Fool energy analyst Joel South takes a question from a reader, who asks, "Why is Northern Tier Energy (UNKNOWN:NTI.DL) plunging? Is it because of the narrowing spread between WTI and WCS? Or the planned cracking unit shutdown in October? Is this a buying opportunity?"

Alison Southwick owns shares of CVR Partners, LP. Joel South has no position in any stocks mentioned. Taylor Muckerman has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not 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.