Pump prices fell just over 16 cents last week as Goldman warns a diesel export ban could lift gasoline

Pump prices fell just over 16 cents a gallon in the past week. For a retailer, a drop that fast is usually a good week on the forecourt, because the street price comes down slower than the cost of the fuel sitting behind it.

Pump margins

Operators hold their street price as long as the competition lets them, so the pump comes down slower than the cost behind it. The gap between the two is the operator's fuel margin. A 16-cent move at the pump in one week points to an even sharper drop at the rack the week before, and the operator who held his street price a day or two longer kept the spread.

The math runs the other way when prices climb. If cost jumps and the competition holds the street down, fuel margin gets thin quick, sometimes to nothing. Falling weeks are the ones retailers bank. Last week was one of them, and the operators who didn't race each other to the bottom on the sign made real money on volume they were going to sell anyway.

The diesel export ban

Goldman Sachs is warning that a US ban on diesel exports could end up pushing gasoline prices higher. Washington has floated suspending diesel exports for 90 days. Goldman's read: once a ban takes effect, it could pull diesel prices down by about 25 cents a gallon each week, but only until domestic storage fills.

Then it turns. Diesel that can't ship overseas and can't fit in a tank has to go somewhere, and the release valve is refinery runs. When refiners throttle back to stop drowning in unsold diesel, they make less gasoline in the same barrel. Less gasoline coming out of the refinery could push pump prices up a few weeks after the ban was supposed to be a diesel story. For a truck stop or a hauler buying diesel by the load, a short-term price break looks nice until storage tops out and the whole thing swings back. For the gasoline island, a policy aimed at diesel could still land on the price sign.

This is a warning, not a schedule. The suspension is still a report, not a rule, and Goldman's numbers only matter if Washington actually pulls the trigger.

Foodservice and loyalty

Cheaper gas leaves a little more in the customer's pocket by the time they reach the counter. Every cent off the pump is money that stayed local, and some of it walks inside for coffee, a roller-grill lunch, a fountain drink. Foodservice carries the margin that fuel never will, and a cheaper fill-up gives the operator a better shot at the inside sale. A driver who spent less at the pump is an easier upsell on a breakfast sandwich.

Loyalty ties the two together. A cents-off-per-gallon reward pins the pump to the basket, and a week of falling street prices is a cheap week to remind customers the points are sitting there. The discount costs the retailer about the same whether the base price is high or low, but it pulls the same traffic through the door, and traffic through the door is what the inside P&L runs on.

What to watch

Whether Washington moves on the 90-day diesel export suspension, and when. The Goldman warning only bites if the ban actually happens, so the report itself changes nothing on your forecourt yet. If it does happen, watch diesel storage, because Goldman's whole call turns on the day tanks fill and refiners start cutting runs. At that point a diesel price break could turn into higher gasoline prices.

Watch your own street price against the rack this week. If wholesale keeps sliding, the margin is there for the operator who doesn't chase the sign down too fast. And watch the inside numbers on the cheaper-gas weeks, because a fill-up that costs less is the best chance you get to move the customer from the pump to the counter.