If you only looked at crude oil inventories, you'd think everything was fine. US commercial crude stocks have built 36 million barrels in 10 weeks — from 420 million in early January to 456 million by mid-March. Days of supply rose from 24.8 to 28.1. We have more crude than we've had in months.
And yet gasoline prices are spiking. The national average is up 40+ cents since February. How is that possible when we're sitting on a mountain of oil?
The answer: we have the wrong oil.
The Bottleneck
US Gulf Coast refineries — the backbone of American fuel production — are designed to process heavy sour crude. This is the thick, sulfur-rich oil that comes from the Middle East, Venezuela, and Canada's oil sands. Over decades, refiners invested billions to configure their equipment specifically for this grade because it's cheaper to buy and more profitable to refine.
What the US produces domestically is mostly light sweet crude — the West Texas Intermediate (WTI) grade. It's chemically different. Running light sweet through a heavy sour refinery is like putting diesel in a gasoline engine. You can do it in limited quantities, but you can't run the whole plant on it efficiently.
When the Strait of Hormuz effectively closed in early March, the heavy sour supply from the Middle East was cut off. Refineries couldn't simply switch to domestic crude. They had to cut throughput.
Refinery input dropped from nearly 17,000 thousand barrels per day in December to 15,661 in late February — a loss of 1.3 million barrels per day of processing capacity. Not because the refineries broke. Because they couldn't get the right feedstock.
The Divergence
This creates a bizarre split: crude inventories build (because there's nowhere for the light sweet oil to go) while gasoline inventories draw (because refineries aren't producing enough fuel).
Look at the gasoline line. From a January peak of 16,642 thousand barrels of finished motor gasoline, stocks plunged to 12,768 by mid-March — the lowest level in over a year.
Why Falling Inventory Means Rising Prices
This is the part that confuses people. If gasoline is being consumed from inventory, doesn't that mean it's available? Why are prices going up?
Think of it like a water tower. The tower holds a reserve of water for the town. The town uses water at a steady rate every day. Normally, the pumps refill the tower as fast as the town drains it. The level stays constant. Water is cheap.
Now the pumps slow down (refinery throughput drops). The town keeps using water at the same rate. The tower level starts falling. The water company sees the level dropping and knows: if this continues, the tower runs dry. So they raise prices to get people to use less — shorter showers, stop watering the lawn. The price increase is the signal that tells people to conserve a shrinking supply.
That's exactly what's happening with gasoline. Refineries are the pumps. Gasoline stocks are the water tower. Americans driving to work are the town. The pumps slowed down (refinery throughput fell 7%), the tower level is dropping (stocks down 23%), and the price is rising ($2.78 → $3.96) to ration what's left.
Nobody panic-bought gas. Gasoline demand in the US is remarkably stable — about 8.5-9.0 million barrels per day, year-round. People drive to work, pick up the kids, go to the grocery store. That doesn't change when oil prices spike. What changed is the supply side. When refineries cut throughput by 1.3 million barrels per day, gasoline production fell below gasoline consumption. The gap came out of inventory. Inventory dropped. Prices rose.
The gas price increase is not demand-driven. It's a refinery configuration problem. America has plenty of oil. It's just the wrong kind for the refineries we built.
Who Benefits From This
The refiners. Specifically, the complex Gulf Coast refiners who can process multiple grades of crude — companies like Valero (VLO), Marathon Petroleum (MPC), and Phillips 66 (PSX).
These companies are buying cheap US light sweet crude (WTI at $89) and selling refined products (gasoline, diesel, jet fuel) at elevated prices because supply is constrained. The crack spread — the difference between crude input cost and refined product value — has blown out. That's pure margin flowing straight to their bottom line.
Meanwhile, the Brent-WTI spread — the price difference between international crude and US domestic crude — has blown out to $14 per barrel. That's another way to see the same story: international crude (the heavy sour kind refineries need) is $14 more expensive than the domestic crude America is swimming in.
When Does This End?
Three scenarios:
Hormuz reopens. Heavy sour crude flows again, refineries ramp back to full throughput, gasoline production normalizes, prices drop. But prediction markets price military action continuing through March at 97%.
Refineries adapt. Some crude units can be adjusted to run more light sweet, but it takes weeks of turnaround time and reduces yields. This is already happening — refinery input has recovered from 15,661 to 16,598 in March. Slow, but trending the right direction.
Canadian heavy crude fills the gap. Canada's oil sands produce heavy crude that Gulf Coast refineries can process. The Trans Mountain pipeline expansion, completed in 2024, added 590,000 barrels per day of capacity. This is the medium-term structural solution, but pipeline logistics take time to ramp.
Until one of these resolves, the spread between crude (abundant) and gasoline (scarce) persists. And the refiners keep printing money.