A crack spread is the difference between the price a refinery pays for crude oil and the price it receives for refined products like gasoline and diesel. It's the single most-watched indicator of refining profitability in the petroleum industry.
The name comes from the refining process itself — "cracking" heavy hydrocarbon molecules in crude oil into lighter, more valuable products. The spread between input cost and output revenue tells you whether refiners are making money.
FuelSignal tracks crack spreads daily using live futures data. View the current crack spread →
The 3-2-1 Crack Spread Formula
The industry standard is the 3-2-1 crack spread. It models a refinery that converts 3 barrels of crude oil into 2 barrels of gasoline and 1 barrel of diesel. This ratio roughly mirrors U.S. refinery output.
The formula:
3-2-1 Crack Spread = (2 × Gasoline Price + 1 × Diesel Price − 3 × Crude Price) ÷ 3
All prices must be in the same unit — dollars per barrel. Since gasoline (RBOB) and diesel (heating oil/ULSD) futures trade in dollars per gallon, you multiply by 42 (gallons per barrel) to convert.
A worked example with real numbers
Using recent futures prices:
- WTI Crude Oil: $65.69/bbl
- RBOB Gasoline: $2.25/gal → $94.70/bbl
- Heating Oil (ULSD): $2.54/gal → $106.88/bbl
Plugging into the formula:
(2 × $94.70 + 1 × $106.88 − 3 × $65.69) ÷ 3 = $33.07/bbl
That's a strong margin. The refinery earns roughly $33 of gross profit per barrel of crude processed.
Gasoline Crack vs. Diesel Crack
The 3-2-1 blends gasoline and diesel into one number. But the two products have different economics and different drivers. Breaking them apart reveals more.
Gasoline crack spread
The simple gasoline crack = RBOB price ($/bbl) minus crude price ($/bbl).
Gasoline cracks are seasonal. They widen in spring and summer as driving demand increases, and tighten in fall and winter. A healthy gasoline crack typically ranges from $8 to $20/bbl. Above $25 signals tight supply or strong demand. Below $5 signals trouble.
Diesel crack spread
The simple diesel crack = heating oil/ULSD price ($/bbl) minus crude price ($/bbl).
Diesel cracks tend to be higher and more volatile than gasoline cracks. Diesel demand is driven by freight, construction, and heating — less seasonal, more tied to economic activity. Cold snaps spike diesel cracks sharply. A healthy diesel crack is $12 to $30/bbl.
Why the split matters
A refiner with a complex configuration that can swing output between gasoline and diesel has a real advantage. When gas cracks are strong, they maximize gasoline yield. When diesel cracks spike, they shift to distillate. Watching both cracks — not just the blended 3-2-1 — tells you which product is driving margins.
What Drives Crack Spreads
Crack spreads are a function of crude supply, product demand, and refinery capacity. Here are the major drivers:
1. Crude oil prices
Crude is the cost side of the equation. When crude prices fall faster than product prices, crack spreads widen. When crude spikes without a corresponding product price increase, cracks compress. This is why U.S. refiners benefit from the WTI-Brent spread — cheaper domestic crude means fatter margins.
2. Seasonal demand patterns
Gasoline demand peaks in summer (June–August). Refiners ramp up ahead of driving season, tightening crude supply and widening gas cracks. Diesel demand peaks in winter for heating oil and stays steady year-round from freight. The shoulder months (October, March) are typically weakest for combined cracks.
3. Refinery utilization
When refinery utilization is high (above 90%), the system is running near capacity. Any disruption — a turnaround, an outage, a hurricane — immediately tightens product supply and spikes crack spreads. When utilization drops (below 85%), there's spare capacity and product supply is abundant, compressing margins.
FuelSignal tracks refinery utilization weekly alongside crack spreads so you can see both sides of the equation.
4. Refinery outages and turnarounds
Planned turnarounds (maintenance shutdowns) reduce capacity for weeks. Unplanned outages — fires, equipment failures, storms — can take units offline for months. Both tighten product supply in their region and push crack spreads higher.
Hurricane season (June–November) is the biggest risk for Gulf Coast refining capacity, which accounts for roughly half of U.S. refining throughput.
5. Inventory levels
Crude oil and gasoline inventory levels are the supply buffer. When inventories are below the five-year average, the market is tight and crack spreads tend to be higher. When inventories build above normal, supply is abundant and margins compress.
The EIA publishes weekly inventory data every Wednesday. Draws (inventory declines) are bullish for cracks. Builds are bearish.
6. Regulation
Summer-grade gasoline (required May–September in many states) is more expensive to produce, which supports gasoline cracks during the summer blend switch. The Renewable Fuel Standard (RFS) adds compliance costs. Emissions regulations that force refinery closures reduce capacity and structurally support wider spreads.
How to Interpret Crack Spread Levels
Not all crack spread levels mean the same thing. Context matters, but here are rough benchmarks for the 3-2-1:
- Above $25/bbl: Excellent margins. Refiners are generating strong free cash flow. This level is often driven by tight supply (low inventories, high utilization, outages) or strong seasonal demand.
- $15–$25/bbl: Healthy margins. Refiners are profitable and covering capital costs. This is the normal operating range for most of the cycle.
- $10–$15/bbl: Marginal. Smaller, less efficient refiners start to struggle. Complex refiners with access to cheap crude (WTI, heavy Canadian) still do okay.
- Below $10/bbl: Margin pressure. At this level, some refiners may cut throughput or delay maintenance to preserve cash. Extended periods below $10 lead to capacity rationalization — permanent closures of the weakest plants.
Important: the 3-2-1 is a gross margin indicator. It doesn't account for operating costs (energy, labor, maintenance), which typically run $4–$8/bbl. A $12 crack spread sounds decent until you subtract $6/bbl of opex — that's only $6/bbl net.
Crack Spreads and the Full Value Chain
Crack spreads sit at the center of the fuel value chain. Here's how they connect to other indicators:
- Upstream: Rising crude prices compress cracks (unless product prices keep pace). The WTI-Brent spread determines the feedstock cost advantage for U.S. refiners vs. international competitors.
- Refining: The crack spread itself. Refinery utilization, outages, and turnarounds are the supply-side driver.
- Retail: The gap between wholesale gasoline (RBOB) and the pump price is the retail fuel margin. When crack spreads spike, wholesale prices rise. Whether and how fast retailers pass that through determines who captures the margin.
FuelSignal's Market Indicators section tracks all of these in one view — crack spreads, WTI-Brent spread, retail fuel margin, supply balance, and sector breadth.
Who Uses Crack Spreads
Refinery operators
Crack spreads directly determine profitability. Operators use them to decide throughput levels, plan turnaround timing, and hedge margin exposure using futures contracts (buying crude futures, selling product futures).
Fuel retailers
Wholesale gasoline prices — the output side of the crack spread — determine what retailers pay for product. When cracks widen, wholesale costs rise. Retailers must decide how quickly to pass higher costs to consumers or absorb the hit to defend volume.
Energy investors
Crack spreads are the leading indicator for refinery stock earnings. When cracks are strong, expect earnings beats from Marathon Petroleum, Valero, and Phillips 66. When cracks compress, expect misses and guidance cuts. The correlation between crack spreads and refining stock prices is tight.
Analysts and policymakers
Crack spreads explain why gasoline prices move the way they do. When politicians demand answers for high pump prices, the crack spread tells you whether the cost is at the crude level (OPEC, geopolitics), the refining level (capacity, outages), or the retail level (margins, taxes).
Variations Beyond 3-2-1
The 3-2-1 is the most common crack spread, but it's not the only one:
- 5-3-2: 5 barrels crude → 3 barrels gasoline + 2 barrels diesel. Used for refineries with higher distillate output.
- 2-1-1: 2 barrels crude → 1 barrel gasoline + 1 barrel diesel. Simpler split.
- 1-1 cracks: Single-product cracks (gasoline-only or diesel-only). Useful for isolating product-specific margins.
- Brent-based cracks: For European and Asian refiners. Uses Brent crude instead of WTI as the input.
FuelSignal calculates the standard 3-2-1 using WTI crude and Gulf Coast product prices. We also break out the gasoline crack and diesel crack separately.
Track Crack Spreads Daily
Crack spread data is typically scattered across multiple sources — CME for futures, EIA for spot prices, individual refiner earnings for realized margins. FuelSignal aggregates these into a single view, updated daily.
On the Market Data page, you'll find:
- Live 3-2-1 crack spread with 90-day history chart
- Gasoline crack and diesel crack, broken out separately
- The underlying prices: WTI, RBOB, and heating oil futures
- Supply context: crude oil stocks, gasoline stocks, refinery utilization
- Computed indicators: WTI-Brent spread, retail fuel margin, supply balance
The crack spread is the number. Everything else — inventory, utilization, seasonal patterns — is the context that tells you where it's going next.