What Fuel Does an Internal Combustion Engine Use?

Internal combustion (IC) engines run on a range of fuels—most commonly gasoline (petrol) or diesel—though many are designed for natural gas, LPG/propane, ethanol blends, biodiesel/renewable diesel, kerosene-based jet fuel, heavy fuel oil, and, increasingly, alternatives like hydrogen or methanol. The correct fuel depends on the engine’s design and certification; always follow the fuel specified on the filler cap/manual for your specific engine to avoid damage and safety risks. This article explains how engine type dictates fuel choice, what fuels are used by sector, and how to match fuel to an engine safely and legally.

Why Fuel Choice Depends on Engine Design

IC engines convert the chemical energy of a fuel into mechanical work by burning (combusting) it inside a cylinder. The fuel that works—and is safe—depends on how the engine initiates combustion and on the fuel system’s materials and calibration. Spark-ignition (SI) engines ignite a pre-mixed air–fuel charge with a spark and therefore need high-octane, volatile fuels such as gasoline or certain alcohol blends to resist knock. Compression-ignition (CI) engines rely on high compression to ignite injected fuel and therefore need high-cetane, less volatile fuels such as diesel or paraffinic renewable diesel. Gas engines use gaseous fuels (e.g., methane in CNG/LNG, LPG/propane) metered to the intake or injected directly. Aviation turbines burn kerosene-based jet fuel, and large marine engines may run on very low sulfur fuel oils, LNG, or emerging alternatives. Mismatching fuel and engine type can cause knock, misfire, injector/pump damage, or regulatory non-compliance.

Common Fuels by Application

The fuels used in IC engines vary by vehicle/equipment segment and regional regulations. The following list outlines typical fuels by application, noting that local standards and manufacturer approvals apply.

• Passenger cars and light vans: Gasoline (often with up to 10% ethanol, e.g., E10; some regions permit E15 for compatible vehicles); flex-fuel models may use high-ethanol blends such as E85. Diesel models use conventional diesel, biodiesel blends (e.g., up to B7–B20 where allowed), or drop-in renewable diesel (HVO/EN 15940/ASTM D975-eligible).
• Motorcycles, scooters, and small outdoor power equipment: Gasoline (often E10). Many 2-stroke engines require a gasoline–oil premix. Alkylate gasoline is sometimes used to reduce deposits and emissions.
• Heavy-duty trucks, buses, and off-road equipment: Diesel (ULSD), biodiesel blends per OEM limits, renewable diesel (HVO). Some fleets use CNG or LNG; a smaller share uses LPG/propane.
• Aviation piston engines: Aviation gasoline (avgas), historically 100LL (leaded). Unleaded avgas options (e.g., G100UL via STC in the U.S.) are rolling out; use only fuels approved for the specific aircraft/engine.
• Aviation turbines: Jet-A/Jet A-1 (kerosene). Sustainable Aviation Fuel (SAF) that meets ASTM D7566 can be blended (typically up to 50%) with Jet-A as a drop-in; 100% SAF is under testing and limited approvals.
• Marine: Marine diesel oil (MDO), very low sulfur fuel oil (VLSFO) under IMO 2020 rules, LNG for dual-fuel ships, and growing adoption of methanol; heavy fuel oil persists in some contexts with exhaust treatment where allowed.
• Stationary power/industrial engines: Pipeline natural gas, biogas/landfill gas, propane, diesel, renewable diesel, and syngas depending on site and permitting.

These categories reflect dominant practice; however, always verify local fuel standards (ASTM/EN/ISO), emissions rules, and manufacturer approvals before selecting a fuel for any specific engine.

Alternative and Lower-Carbon Fuels You’ll See More Often

Decarbonization and air-quality policies are expanding the use of alternative fuels in IC engines. The items below summarize notable options and their typical use cases or constraints.

• Hydrogen (H2): Can power modified ICEs (especially lean-burn SI or dual-fuel concepts). Offers zero CO2 at the tailpipe but NOx control and onboard storage are key challenges.
• Ammonia (NH3): Investigated for large marine ICEs due to energy density and carbon-free molecule; requires measures for toxicity, NOx mitigation, and reliable ignition.
• Methanol: Liquid at ambient conditions, increasingly used in marine dual-fuel engines; simpler storage than LNG, lower flash point than diesel, and different materials compatibility.
• Ethanol: Common in blends with gasoline (E10 widespread; higher blends like E85 for flex-fuel engines). Raises octane but has lower energy density and can affect cold starts and materials in non-compatible systems.
• Biodiesel (FAME): Fatty acid methyl esters blended with diesel (e.g., B5–B20 depending on OEM/regional limits). Renewable, with higher cetane but potential cold-flow and oxidation stability concerns.
• Renewable diesel (HVO): Hydrotreated vegetable oil or similar paraffinic diesel. Drop-in for many diesel engines with good cold properties and low aromatics; typically meets EN 15940 and can be sold as ASTM D975 diesel.
• Biomethane/biogas: Upgraded biogas used in gas engines or injected into gas grids; often requires cleanup (e.g., H2S removal) for engine durability.
• Power-to-liquid “e-fuels”: Synthetic gasoline/diesel/kerosene made from captured CO2 and green hydrogen; designed as drop-in fuels meeting existing specs; currently limited supply and higher cost.
• Sustainable Aviation Fuel (SAF): Various pathways (HEFA, ATJ, FT) certified under ASTM D7566; blended with Jet-A for use in turbine engines; scaling up globally.

Availability, infrastructure, and engine approvals vary widely. Using these fuels safely and without voiding warranties requires adherence to published fuel standards and OEM guidance.

How to Match the Right Fuel to Your Engine

Ensuring the correct fuel is as much about safety and compliance as it is about performance. Use the following checklist to identify the right fuel for any engine.

1. Consult the owner’s manual, filler cap, or OEM service bulletin for the exact approved fuel(s) and blend limits.
2. Identify engine type: spark-ignition (gasoline/gaseous) vs. compression-ignition (diesel) or turbine, as each has specific fuel requirements.
3. Check grade/spec: For gasoline, use the required octane (RON/AKI). For diesel, ensure the correct cetane rating and standard (ASTM D975, EN 590, EN 15940, etc.).
4. Confirm regional blends: Know the local norm (e.g., E10 gasoline, winter/summer RVP, seasonal diesel grades) and your vehicle’s compatibility with higher ethanol or biodiesel blends.
5. For diesel engines, verify allowable biodiesel content, cold-flow requirements, and whether renewable diesel is approved as drop-in.
6. For gas-fueled engines (CNG/LNG/LPG), confirm pressure, composition, and any required filtration or lubricity additives per OEM.
7. For aviation and marine engines, use only certified fuels and adhere to type certificates, STCs, class rules, and port-state regulations.
8. Avoid misfueling: Never put gasoline into a diesel engine or vice versa; label containers and dispensers clearly.
9. When in doubt, contact the manufacturer or a certified service center before switching fuels or blends.

Following these steps helps protect the engine, maintain emissions compliance, and reduce the risk of costly repairs or safety incidents.

Fuel Properties That Matter for Engine Performance and Durability

Different fuels bring different chemistries and performance traits. Understanding the key properties explains why certain engines require specific fuels.

• Octane rating (gasoline/alcohols): Resistance to knock in SI engines; higher octane allows higher compression/boost.
• Cetane number (diesel/paraffinics): Ignition quality in CI engines; higher cetane improves cold starts and reduces ignition delay.
• Energy density: Affects range and fuel economy; diesel generally has higher volumetric energy density than gasoline; alcohols are lower.
• Volatility and vapor pressure: Critical for cold starts and hot-soak behavior in SI engines; regulated seasonally.
• Lubricity and viscosity: Important for diesel injection equipment longevity; ultra-low sulfur diesel often needs lubricity additives.
• Sulfur and aromatics content: Impacts emissions control systems and particulate formation.
• Oxygen content: Can aid cleaner combustion but affects stoichiometry and fuel economy.
• Cold-flow properties (cloud/pour/CFPP): Dictate winter operability of diesel and some paraffinic fuels.
• Materials compatibility: Alcohols and some synthetic fuels can affect seals, hoses, and tanks not designed for them.
• Emissions profile: Fuels differ in NOx, PM, CO, and unburned hydrocarbons; aftertreatment systems are calibrated accordingly.

Matching these properties to engine design is central to reliable operation, meeting emissions standards, and achieving intended performance.

Safety and Storage Considerations

Proper handling and storage protect both users and equipment. Observe the following best practices for common fuels.

• Use approved, clearly labeled containers; separate gasoline and diesel cans to prevent misfueling.
• Store fuels in cool, ventilated areas away from ignition sources; follow local fire codes.
• Mind shelf life: Unstabilized gasoline can degrade in 3–6 months; diesel lasts longer but may need biocides and water management; renewable diesel (HVO) generally stores well; ethanol blends absorb moisture.
• Add fuel stabilizer for seasonal equipment and run the engine briefly to circulate it.
• Inspect CNG/LNG/LPG cylinders and lines per codes; never tamper with pressure relief devices.
• For aviation and marine fuels, adhere to strict contamination controls and filtration procedures.
• Prepare for spills with absorbents and follow environmental reporting rules if releases occur.

Thoughtful storage and handling reduce hazards, extend fuel life, and prevent damage to fuel systems and emissions controls.

Summary

IC engines don’t use a single universal fuel: gasoline and diesel dominate road transport, while gaseous fuels, kerosenes, and various oils serve aviation, marine, and stationary roles. The correct choice depends on engine type (spark vs. compression ignition vs. turbine), manufacturer approvals, and local fuel standards. Alternatives such as renewable diesel, SAF, methanol, and hydrogen are expanding but require specific certifications and infrastructure. When selecting a fuel for any engine, rely on the OEM’s guidance and relevant fuel specifications to ensure safety, compliance, and performance.

What fuels can run an internal combustion engine?

Internal combustion engines provide outstanding drivability and durability, with more than 250 million highway transportation vehicles in the United States relying on them. Along with gasoline or diesel, they can also utilize renewable or alternative fuels (e.g., natural gas, propane, biodiesel, or ethanol).

Is a CI engine petrol or diesel?

The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is called a compression-ignition engine (or CI engine).

Which fuel Cannot be used in IC engine?

Explanation: Alcohols have high self-ignition temperature and low latent heat of vaporization. That is why they cannot be used in CI engines.

What is the fuel used in IC engine?

ICEs are typically powered by hydrocarbon-based fuels like natural gas, gasoline, diesel fuel, or ethanol. Renewable fuels like biodiesel are used in compression ignition (CI) engines and bioethanol or ETBE (ethyl tert-butyl ether) produced from bioethanol in spark ignition (SI) engines.