What is the sweet-sour crude spread?

The sweet-sour crude spread is the price differential between light sweet crude oil (low sulphur content, 1.5% sulphur). Sweet crude benchmarks: WTI (0.24% sulphur), Brent (0.37% sulphur). Sour crude benchmarks: Dubai/Oman (~2% sulphur), Arab Heavy (~2.8% sulphur), Urals (~1.7% sulphur). The spread reflects: (1) the additional refining cost to desulphurise sour crude (hydrodesulphurisation units, hydrogen consumption); (2) the higher yield of gasoline and jet fuel from sweet crude; (3) sulphur regulations on finished products (IMO 2020 for marine fuels; EURO 6 for road fuels) which increase the premium for low-sulphur feedstock. The sweet premium over sour crude typically ranges from $2–8/barrel, widening when sulphur product specs tighten.

What is the difference between sweet and sour crude oil?

Sweet crude oil contains less than 0.5% sulphur by weight; sour crude contains more than 0.5% sulphur (with heavily sour grades at 2–3%+). The 'sweet' designation comes from the pleasant taste/smell of low-sulphur crude vs the sulphurous 'sour' smell of high-sulphur crude — a historical sensory test. Beyond sulphur, crude oil quality is also classified by API gravity: light crude (API >31.1°) vs heavy crude (API <22.3°). The most valuable crudes are 'light sweet' — high API gravity + low sulphur — which yield maximum gasoline, jet fuel, and diesel with minimum processing. 'Heavy sour' crudes (e.g. Canadian oil sands, Venezuelan Orinoco belt, Arab Heavy) require the most sophisticated refining — hydrocracking and desulphurisation — but are priced at a large discount, making them attractive to complex refineries.

How did IMO 2020 affect the sweet-sour crude spread?

IMO 2020 (effective January 2020) capped sulphur in marine bunker fuel at 0.5% (from 3.5%), sharply increasing demand for low-sulphur fuel oil (LSFO) and directly affecting crude quality economics. Effects on the sweet-sour spread: (1) Pre-IMO 2020 (2018–2019): the anticipated sulphur cap caused the spread to widen significantly — sour crude discounts deepened as demand for high-sulphur fuel oil (HSFO) was expected to collapse; (2) Post-IMO 2020 implementation: the spread moderated as complex refiners could process sour crude into low-sulphur products (using hydrodesulphurisation); HSFO volumes fell but were replaced by VLSFO (very low sulphur fuel oil); (3) Russian Urals discount: post-2022 Russia sanctions significantly widened the Urals-Brent differential (from ~$2/bbl to $20–30/bbl at peak), as Urals (a medium sour crude) was embargoed by European buyers — distorting typical sweet-sour spread relationships with a geopolitical discount.

Sweet–Sour Crude Spread

Q: How did IMO 2020 affect the sweet-sour crude spread?

IMO 2020 (effective January 2020) capped sulphur in marine bunker fuel at 0.5% (from 3.5%), sharply increasing demand for low-sulphur fuel oil (LSFO) and directly affecting crude quality economics. Effects on the sweet-sour spread: (1) Pre-IMO 2020 (2018–2019): the anticipated sulphur cap caused the spread to widen significantly — sour crude discounts deepened as demand for high-sulphur fuel oil (HSFO) was expected to collapse; (2) Post-IMO 2020 implementation: the spread moderated as complex refiners could process sour crude into low-sulphur products (using hydrodesulphurisation); HSFO volumes fell but were replaced by VLSFO (very low sulphur fuel oil); (3) Russian Urals discount: post-2022 Russia sanctions significantly widened the Urals-Brent differential (from ~$2/bbl to $20–30/bbl at peak), as Urals (a medium sour crude) was embargoed by European buyers — distorting typical sweet-sour spread relationships with a geopolitical discount.

The price premium of low-sulphur sweet crude over high-sulphur sour crude — a key signal of refining economics and sulphur product regulations.

Published 1 October 2026 · Updated 22 October 2026

Definition

The sweet–sour crude spread is the price differential between light sweet crude oil (typically <0.5% sulphur) and heavier sour crude oil (typically >1.0–2.5% sulphur). Sweet crude fetches a premium because it: (1) yields more high-value light products (gasoline, jet fuel, naphtha) per barrel; (2) requires less processing — fewer hydrodesulphurisation (HDS) units, less hydrogen consumption; (3) meets tighter sulphur specifications in finished products without costly refining steps.

Crude	API gravity	Sulphur (%)	Classification	Benchmark price basis
WTI (West Texas Intermediate)	~39.6°	~0.24%	Light sweet	NYMEX futures; US benchmark
Brent	~38.3°	~0.37%	Light sweet	ICE Brent; global reference
Dubai/Oman	~31°	~2.0%	Medium sour	Middle East sour benchmark
Arab Light	~33°	~1.77%	Medium sour	Saudi Aramco OSP reference
Arab Heavy	~27°	~2.80%	Heavy sour	Deepest Middle East discount
Urals	~31.7°	~1.75%	Medium sour	European/Russian reference; large discount post-2022
Forties (Brent blend)	~40°	~0.60%	Light slightly sour	Brent physical component

What drives the sweet–sour spread?

Refining economics and desulphurisation costs Processing sour crude requires hydrodesulphurisation (HDS) units that consume hydrogen (typically produced by steam methane reforming of natural gas). Higher sulphur crude requires more HDS capacity, more hydrogen, and more refinery capital investment. A complex refinery (Nelson Complexity Index 12–16) can process the sourest crudes economically; a simpler hydroskimming refinery (NCI 2–4) cannot handle heavy sour crudes at all — limiting its crude diet to light sweet grades. The spread reflects the market value of avoiding HDS costs and capturing better product yields. For refinery economics explained, see our oil refinery economics guide.: Processing sour crude requires hydrodesulphurisation (HDS) units that consume hydrogen (typically produced by steam methane reforming of natural gas). Higher sulphur crude requires more HDS capacity, more hydrogen, and more refinery capital investment. A complex refinery (Nelson Complexity Index 12–16) can process the sourest crudes economically; a simpler hydroskimming refinery (NCI 2–4) cannot handle heavy sour crudes at all — limiting its crude diet to light sweet grades. The spread reflects the market value of avoiding HDS costs and capturing better product yields. For refinery economics explained, see our oil refinery economics guide.
Product sulphur regulations Finished fuel sulphur specifications have progressively tightened: road diesel (10 ppm sulphur in EU/US), gasoline (10 ppm EU), marine VLSFO (0.5% sulphur max from IMO 2020). As product sulphur limits fall, the refining cost of desulphurisation rises, increasing the value of low-sulphur feedstocks. IMO 2020 was a major driver — it sharply reduced the value of high-sulphur fuel oil (HSFO), a key by-product of sour crude refining without hydrocracking.: Finished fuel sulphur specifications have progressively tightened: road diesel (10 ppm sulphur in EU/US), gasoline (10 ppm EU), marine VLSFO (0.5% sulphur max from IMO 2020). As product sulphur limits fall, the refining cost of desulphurisation rises, increasing the value of low-sulphur feedstocks. IMO 2020 was a major driver — it sharply reduced the value of high-sulphur fuel oil (HSFO), a key by-product of sour crude refining without hydrocracking.
OPEC+ production and sour crude availability Most Middle Eastern OPEC+ crude is medium-to-heavy sour (Arab Light, Arab Heavy, Kuwait, Basra). When OPEC+ cuts production, sour crude supply falls — narrowing the sweet-sour spread (because sour supply becomes relatively tighter vs sweet). When US shale (light sweet) production rises rapidly (2018–2019), sweet crude supply glut narrows the sweet premium. The current OPEC+ strategy of volume restraint has kept Middle Eastern sour crudes relatively tight, supporting a narrower-than-historical sweet premium of ~$2–5/bbl.: Most Middle Eastern OPEC+ crude is medium-to-heavy sour (Arab Light, Arab Heavy, Kuwait, Basra). When OPEC+ cuts production, sour crude supply falls — narrowing the sweet-sour spread (because sour supply becomes relatively tighter vs sweet). When US shale (light sweet) production rises rapidly (2018–2019), sweet crude supply glut narrows the sweet premium. The current OPEC+ strategy of volume restraint has kept Middle Eastern sour crudes relatively tight, supporting a narrower-than-historical sweet premium of ~$2–5/bbl.
Russian Urals: geopolitical discount vs quality discount Russia's Urals crude (medium sour, ~1.75% S) historically traded at $2–3/bbl discount to Brent — primarily a quality discount. Post-February 2022 Russia sanctions, Urals' discount to Brent widened dramatically — to $25–35/bbl at peak — driven by European buyers switching to alternative suppliers. By 2024–2026, Urals normalised to a $10–15/bbl discount as Asian buyers (India, China) absorbed Russian crude at discounted prices. This geopolitical distortion decoupled Urals from the normal sweet-sour spread calculation. For Iraq's sour crude production (a Urals substitute for some refiners), see our Iraq oil production 2026.: Russia's Urals crude (medium sour, ~1.75% S) historically traded at $2–3/bbl discount to Brent — primarily a quality discount. Post-February 2022 Russia sanctions, Urals' discount to Brent widened dramatically — to $25–35/bbl at peak — driven by European buyers switching to alternative suppliers. By 2024–2026, Urals normalised to a $10–15/bbl discount as Asian buyers (India, China) absorbed Russian crude at discounted prices. This geopolitical distortion decoupled Urals from the normal sweet-sour spread calculation. For Iraq's sour crude production (a Urals substitute for some refiners), see our Iraq oil production 2026.

Sweet–sour spread historical context

Period	Brent–Dubai spread approx.	Key driver
2015–2016	$2–4/bbl	Light tight oil (LTO) supply glut; compressed sweet premium
2017–2018	$3–6/bbl	Venezuelan/Iranian sour supply disruptions
2019 (pre-IMO 2020)	$5–9/bbl	IMO 2020 anticipation; HSFO value collapse
2020 (COVID)	$2–4/bbl	Demand destruction; spread compression
2021–2022	$3–7/bbl	Recovery; Russia sanctions distorting Urals (not Brent-Dubai)
2023–2026	$2–5/bbl	OPEC+ sour cuts keeping Middle East sour tight; normalised range

For crude benchmarks and WTI–Brent relationship, see our WTI crude glossary entry and Brent crude glossary entry. For refining crack spreads context, see our oil refinery economics guide.

Frequently asked questions

What is the sweet-sour crude spread? The sweet-sour spread is the price premium of low-sulphur sweet crude (Brent, WTI: <0.5% S) over high-sulphur sour crude (Dubai, Arab Heavy: 2–3% S). The spread reflects refining desulphurisation costs, product yield differences, and sulphur regulations on finished fuels. Typical range: $2–8/bbl Brent-Dubai. IMO 2020 and Russian sanctions have significantly influenced recent spreads.: The sweet-sour spread is the price premium of low-sulphur sweet crude (Brent, WTI: <0.5% S) over high-sulphur sour crude (Dubai, Arab Heavy: 2–3% S). The spread reflects refining desulphurisation costs, product yield differences, and sulphur regulations on finished fuels. Typical range: $2–8/bbl Brent-Dubai. IMO 2020 and Russian sanctions have significantly influenced recent spreads.
What is the difference between sweet and sour crude oil? Sweet crude: <0.5% sulphur; high API gravity (light); minimal desulphurisation needed; high gasoline/jet yield. Examples: WTI (0.24% S, 39.6° API), Brent (0.37% S). Sour crude: >0.5% sulphur (often 1.5–3%); lower API gravity; requires extensive hydrodesulphurisation; traded at discount. Examples: Dubai (2% S), Arab Heavy (2.8% S), Urals (1.75% S). "Sweet" and "sour" are historical sensory terms for low and high sulphur content.: Sweet crude: <0.5% sulphur; high API gravity (light); minimal desulphurisation needed; high gasoline/jet yield. Examples: WTI (0.24% S, 39.6° API), Brent (0.37% S). Sour crude: >0.5% sulphur (often 1.5–3%); lower API gravity; requires extensive hydrodesulphurisation; traded at discount. Examples: Dubai (2% S), Arab Heavy (2.8% S), Urals (1.75% S). "Sweet" and "sour" are historical sensory terms for low and high sulphur content.
How did IMO 2020 affect the sweet-sour crude spread? IMO 2020 (0.5% sulphur cap on marine bunker fuel from Jan 2020) widened the sweet premium in 2018–2019 as HSFO — a by-product of sour crude refining — lost value. Post-implementation, complex refiners using hydrodesulphurisation could still profitably process sour crude into VLSFO and other low-S products, moderating the spread. Russian Urals sanctions (2022+) added a separate geopolitical discount of $10–30/bbl on Urals — larger than the normal quality spread.: IMO 2020 (0.5% sulphur cap on marine bunker fuel from Jan 2020) widened the sweet premium in 2018–2019 as HSFO — a by-product of sour crude refining — lost value. Post-implementation, complex refiners using hydrodesulphurisation could still profitably process sour crude into VLSFO and other low-S products, moderating the spread. Russian Urals sanctions (2022+) added a separate geopolitical discount of $10–30/bbl on Urals — larger than the normal quality spread.