Crude oil is a naturally occurring liquid hydrocarbon mixture found in geological formations beneath the Earth's surface. It is composed primarily of carbon and hydrogen atoms arranged in chains and rings of varying lengths — from light gaseous components (methane, ethane) to heavy waxy compounds (paraffins, asphaltenes). Crude oil is the raw feedstock for petroleum refining — it is processed in refineries to produce petrol (gasoline), diesel, jet fuel, heating oil, LPG, naphtha, bitumen, and other products. World crude oil production is approximately 100 million barrels per day (mb/d), making it the single largest source of primary energy globally.

What is API gravity in crude oil?

API gravity is a measure of crude oil density on a scale where water = 10° API. Higher API gravity means lighter (less dense) crude. Light crudes (38–42° API, such as Brent or WTI) are more valuable because they yield a higher proportion of high-value products (petrol, diesel, jet fuel) per barrel. Heavy crudes (15–25° API, such as Venezuelan Orinoco Belt or Canadian oil sands) yield more residual fuel oil and require more complex (and expensive) refinery processing to convert heavy fractions into lighter, more valuable products. The API gravity differential between light and heavy crudes typically creates a light crude premium of $5–15/barrel in normal markets.

What percentage of crude oil becomes petrol and diesel?

The yield of petrol and diesel from a barrel of crude depends on the crude type and the complexity of the refinery processing it. A typical modern complex refinery processing light-sweet crude (Brent equivalent) yields approximately: 45–50% gasoil/diesel/heating oil; 25–35% gasoline/petrol; 8–15% jet fuel/kerosene; 4–8% LPG/naphtha; 2–5% residual fuel oil and other. Simple (hydroskimming) refineries produce less petrol and diesel and more residual fuel oil. Complex refineries with catalytic crackers and hydrocrackers convert more heavy fractions into lighter products, maximising diesel and petrol yields.

Crude Oil

The raw hydrocarbon feedstock from which petrol, diesel, jet fuel, and virtually all petroleum products are refined — the world's most traded commodity and the primary driver of fuel prices.

Definition

Crude oil is a naturally occurring liquid mixture of hydrocarbons extracted from geological formations underground. It is the feedstock input to petroleum refining — processed in refineries to produce the full slate of petroleum products used in transport, heating, power generation, and as chemical feedstocks.

Crude oil is the world's most actively traded commodity, with approximately 100 million barrels per day (mb/d) produced globally. Its price — typically quoted in US dollars per barrel for benchmark grades — is the single largest factor in determining the cost of petrol and diesel at the pump. For benchmark grade prices and how they relate to fuel prices, see our crude oil benchmarks guide and our Brent crude glossary entry.

Physical classification: API gravity and sulphur content

All crude grades are characterised by two key quality parameters:

Classification	API gravity	Sulphur (%)	Example grades	Refining complexity required
Light sweet	38–42°	<0.5%	Brent, WTI, Bonny Light	Low — high product yields from simple distillation
Medium sour	28–38°	0.5–2.0%	Arab Light, Urals, Forcados	Medium — requires HDS units for desulphurisation
Heavy sour	20–28°	>2.0%	Arab Heavy, Mars, WCS	High — requires conversion units (FCC, hydrocracker)
Extra heavy / bitumen	<10°	>3.5%	Orinoco Belt, oil sands	Very high — requires upgrading before refining

For the sour crude grades in detail, see our sour crude glossary entry.

Major producing regions and crude types

Region	Production (mb/d, approx. 2025)	Benchmark grade	Grade type
USA (primarily Permian Basin)	~13.5	WTI / WTI Midland	Light sweet
Saudi Arabia	~9–10	Arab Light, Arab Heavy	Medium–heavy sour
Russia	~9	Urals, ESPO	Medium sour / light sweet
Iraq	~4.5	Basra Light, Basra Heavy	Medium–heavy sour
Canada	~5.5	WCS, Synbit	Heavy sour / oil sands
UAE	~3.5	Murban, Upper Zakum	Light–medium sour
North Sea	~1.5	Brent (BFOET)	Light sweet

From crude to fuel: the refining process

Crude oil is not directly usable as fuel. It is separated into component fractions (distillation) and further processed (conversion, treating) in a petroleum refinery. The key steps:

Atmospheric distillation: Crude is heated and vapours are separated by boiling point in an atmospheric distillation column. LPG, naphtha, kerosene, gasoil, and atmospheric residue are produced
Vacuum distillation: Atmospheric residue is distilled under vacuum to produce vacuum gasoil (VGO — a hydrocracker/FCC feedstock) and vacuum residue
Conversion units: FCC (fluid catalytic cracker) or hydrocracker converts VGO into petrol and diesel; coker converts residue
Treating and blending: HDS (hydrodesulphurisation) removes sulphur; reformers boost octane; products are blended to specification

Typical product yield from a complex refinery on light sweet crude: ~30% petrol, ~45% diesel/gasoil, ~10% jet fuel, ~5% LPG, ~5% naphtha, ~5% other. For how refinery processing costs feed into pump prices, see our refinery margin glossary entry and our petrol price per litre guide.

What is crude oil and why does it matter for fuel prices?

What is crude oil? It is a naturally occurring liquid hydrocarbon mixture found underground — the raw feedstock from which petrol, diesel, jet fuel, heating oil, LPG and hundreds of other products are refined. Crude oil is the world's most actively traded commodity, with approximately 100 million barrels produced per day globally. Its price — quoted in US dollars per barrel for benchmark grades such as Brent and WTI — is the single largest factor in determining the cost of fuel at the pump. The U.S. EIA petroleum data portal provides daily price data, production statistics and inventory reports, while the IEA Oil Market Report offers monthly analysis of global supply-demand balances.

The quality of crude oil — measured by API gravity (density) and sulphur content — determines how much petrol, diesel and other valuable products a refinery can extract from each barrel. Light, sweet crudes like Brent and WTI yield more high-value products and command a premium. Heavy, sour crudes require more complex and expensive refinery processing. The OPEC Annual Statistical Bulletin tracks production, reserves and quality data for all major producing countries, and the European Commission's weekly oil bulletin shows how crude price changes flow through to European wholesale and retail fuel prices.

OPEC+ and crude oil supply management

Approximately 40% of global crude oil production is managed by OPEC+ — the expanded Organisation of Petroleum Exporting Countries plus Russia and other allies. OPEC+ coordinates production quotas among members to manage supply and influence prices:

Saudi Arabia (~9–10 mb/d) is the swing producer with the largest spare capacity
OPEC+ production cuts in 2022–2026 supported crude prices during demand uncertainty
Non-OPEC supply growth (primarily US shale) constrains OPEC+'s ability to set prices unilaterally
OPEC+ ministerial meetings (typically biannual) are closely watched crude price catalysts

For how OPEC+ decisions affect retail fuel prices, see our petrol price forecast 2027.

Frequently asked questions

What is crude oil? Crude oil is a naturally occurring liquid hydrocarbon mixture extracted from underground geological formations. It is the raw feedstock for petroleum refining — processed to produce petrol, diesel, jet fuel, heating oil, LPG, naphtha, and petrochemical feedstocks. With ~100 mb/d of global production, crude oil is the world's most traded commodity and the primary driver of fuel pump prices worldwide.: Crude oil is a naturally occurring liquid hydrocarbon mixture extracted from underground geological formations. It is the raw feedstock for petroleum refining — processed to produce petrol, diesel, jet fuel, heating oil, LPG, naphtha, and petrochemical feedstocks. With ~100 mb/d of global production, crude oil is the world's most traded commodity and the primary driver of fuel pump prices worldwide.
What is API gravity in crude oil? API gravity measures crude oil density (water = 10° API). Higher API = lighter crude. Light crudes (38–42° API, like Brent/WTI) are more valuable — they yield more petrol and diesel per barrel and need less complex refining. Heavy crudes (15–25° API) yield more residual fuel oil and require expensive conversion units. Light sweet crude typically commands a $5–15/barrel premium over heavy sour grades.: API gravity measures crude oil density (water = 10° API). Higher API = lighter crude. Light crudes (38–42° API, like Brent/WTI) are more valuable — they yield more petrol and diesel per barrel and need less complex refining. Heavy crudes (15–25° API) yield more residual fuel oil and require expensive conversion units. Light sweet crude typically commands a $5–15/barrel premium over heavy sour grades.
What percentage of crude oil becomes petrol and diesel? From a typical complex refinery processing light sweet crude: approximately 30% petrol/gasoline, 45% diesel/gasoil, 10% jet fuel, 5% LPG, 5% naphtha, 5% other products. Simple (hydroskimming) refineries produce more residual fuel oil and less petrol. The precise yield depends on crude grade, refinery configuration, and desired product mix.: From a typical complex refinery processing light sweet crude: approximately 30% petrol/gasoline, 45% diesel/gasoil, 10% jet fuel, 5% LPG, 5% naphtha, 5% other products. Simple (hydroskimming) refineries produce more residual fuel oil and less petrol. The precise yield depends on crude grade, refinery configuration, and desired product mix.