Diesel street margin is $1.627 a gallon, up 52 cents in a month

The gap between what a station pays for diesel wholesale and what it charges at the pump is $1.627 a gallon. It has widened by about 52 cents over the past 30 days, so a station's gross margin on each gallon is wider now than it was a month ago.

The margin widened while diesel itself ran up. U.S. diesel is $6.382 a gallon, up 14.0 percent over 30 days, and it is near the top of its range for the month, at the 95 percent mark between a $3.459 low and a $6.529 high. Retail followed wholesale up and then kept climbing, and that is where the extra street margin came from. Gasoline did much the same, at $4.603 and sitting at the 99 percent mark of its own 30-day range, close to the $4.628 high.

Refiners widened too. The 3:2:1 crack spread is $64.65 a barrel, up $3.20 over the month, so the margin for turning crude into fuel improved alongside the margin at the pump. Both ends of the chain are earning more per gallon than they were 30 days ago.

One thing to watch is refinery utilization, down 7.1 percent over 30 days and at the 31 percent mark of its range. If runs stay low while demand holds, wholesale diesel could stay firm, which may keep retail prices high even as the current street margin narrows back toward normal. For now the read is simple: diesel is expensive, and the people selling it are keeping more of each gallon than usual.