Get em while they're cheap! You might find cheaper premiums on HFC as they nose-dived yesterday, but MPC has stronger fundamentals IMO.
And a reminder like always, MPC has a history of bucking the market the market: SPY.
In regard to fundamentals, this is an oversold reaction to MPC and other refiners' posting losses for Q1 2016. We all knew the refining margins honeymoon would come to a close eventually. This is a response not in rising crude prices, but rather a response to the lack of rise of gasoline prices (the other leg that makes up the refining crack spread).