Unleaded gasoline is cheap but diesel is not?

I just bought unleaded gas for $1.99 per gallon, but noticed that diesel was $3.55. I thought these were made out of the same basic stuff and are usually priced similarly. Why is diesel so much more expensive? This is in Lexington, KY, in case that matters.

I started the same thread yesterday n GQ.

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Probably not a Great Debate, and already the same question is open in GQ, so closing this.

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