Yes—but changing fast: The internal combustion engine is still widely used in 2025

Yes. Internal combustion engines (ICEs) remain in extensive use across the world today—in cars and trucks, airplanes, ships, trains, construction and farm equipment, and backup power—though their dominance is gradually waning as electric and other zero-emission technologies scale up. Most vehicles on the road still have combustion engines, and even in new sales, combustion (including hybrids) continues to hold a majority share, despite rapid growth in electric vehicles (EVs).

Where internal combustion still dominates

While headlines often focus on electric adoption, the day-to-day reality is that ICE technology remains the backbone of global mobility and many industrial applications. The sectors below illustrate where combustion is still essential or prevalent due to performance needs, infrastructure constraints, and regulatory frameworks.

• Road transport: The global vehicle fleet numbers well over a billion units, the vast majority ICE-powered. Even in 2024, roughly four out of five new cars sold worldwide were still combustion-based (including hybrids), according to the International Energy Agency (IEA).
• Heavy-duty trucking and buses: Diesel remains the workhorse for long-haul freight and many regional routes, with zero-emission models growing from a small base.
• Aviation: Commercial airliners use gas turbines (a form of internal combustion). Battery-electric flight is limited to small aircraft and short training hops; hydrogen and hybrid-electric concepts are in development but not commercialized at scale.
• Maritime shipping: Large cargo and tanker fleets primarily run on diesel and heavy fuel oils, with growing adoption of dual-fuel engines (LNG and methanol) but limited zero-emission alternatives so far.
• Rail: Many networks—especially freight and regional lines outside heavily electrified corridors—use diesel locomotives or diesel-electric hybrids.
• Off-road machinery: Agriculture, mining, and construction rely heavily on diesel ICE for power density and runtime; battery models are emerging for smaller classes and duty cycles.
• Stationary and small engines: Backup generators for data centers and hospitals, remote microgrids, and small equipment (e.g., outboard motors, some lawn tools) still use ICE, though certain jurisdictions are tightening rules on small off-road engines.

These applications reflect a mix of technical demands—high energy density, long range, and rugged duty cycles—and infrastructure realities that keep ICE central to global energy and transport systems today.

Why ICEs persist despite the electric surge

Several practical and economic factors explain why internal combustion remains entrenched even as EVs, fuel cells, and electrified powertrains expand. The following drivers shape adoption timelines across markets and sectors.

• Energy density and refueling speed: Liquid fuels pack high energy per kilogram and enable fast refueling, vital for long-haul logistics and aviation.
• Existing infrastructure: Global networks for fuel production, distribution, and service are mature, reliable, and ubiquitous compared with charging and hydrogen refueling.
• Total cost and product cycles: For many duty cycles (especially heavy-duty and off-road), lifecycle economics of ICE remain competitive, and equipment refresh cycles can exceed a decade.
• Cold climates and remote operations: Performance, range, and heating loads can favor combustion in extreme conditions without robust charging infrastructure.
• Residual value and fleet inertia: A vast installed base means ICE vehicles and machines will remain in service for many years, even as new sales transition.
• Fuel flexibility: ICEs can run on a range of fuels—gasoline, diesel, CNG/LNG, LPG, biofuels, and even hydrogen—allowing incremental decarbonization without entirely new platforms.

Together, these factors slow the pace of change in sectors where performance and uptime are paramount, even as policy and technology steadily push toward cleaner solutions.

How fast is the shift to electrification?

Momentum is strong, particularly in light-duty road transport. The IEA reported that electric cars reached roughly one in five new car sales globally in 2024, up from about one in six in 2023. China, Europe, and the United States lead in volumes, while emerging markets are seeing faster two- and three-wheeler electrification. Battery costs have continued to improve, with industry analyses placing average pack prices in the low-$130s per kWh in 2024, supporting more competitive EV pricing.

Hybrids (HEVs and PHEVs) also grew sharply in 2023–2024, acting as a bridge technology that keeps ICE in the loop while cutting fuel consumption and emissions. In heavy-duty trucking, electric and hydrogen models are ramping but from a small base; total penetration remains low relative to diesel, especially in long-haul applications.

Policy checkpoints and phaseout plans

Governments are tightening emissions standards and setting future sales targets that will reshape the market for new vehicles. The following milestones indicate the regulatory direction, though most focus on new sales rather than removing existing ICE assets.

• European Union: Target of 100% CO2 reduction for new cars by 2035 (effectively zero tailpipe emissions), with a narrow e-fuels exception under specific conditions. Euro 7 pollutant rules were finalized in a softened form compared with early proposals, with staged implementation late this decade.
• United Kingdom: New petrol/diesel car ban moved to 2035; interim zero-emission sales quotas are in place for automakers.
• United States: EPA finalized greenhouse-gas standards for light-duty vehicles for model years 2027–2032, designed to drive a large share of EVs by 2032. California and other states adopting Advanced Clean Cars II target 100% zero-emission new light-vehicle sales by 2035 (with limited PHEV allowances).
• Canada: Mandate for 100% zero-emission new light-duty vehicle sales by 2035, with interim targets.
• China: “NEV” policy framework continues to expand EV share via credit systems; electrification is advancing rapidly in cars and buses, with ambitious industrial policies for batteries and charging.
• Japan: Aims for all new car sales to be “electrified” (including hybrids) by the mid-2030s; hydrogen strategies target heavy transport and industry.
• India: Tightening fuel-efficiency and emissions norms (BS6) and incentives for EVs and two-wheelers; widespread ethanol blending (E20 target) supports partial decarbonization of ICE fuel.

These policies generally regulate new sales, meaning existing combustion vehicles and equipment will remain in service well into the 2030s and 2040s, especially in regions without scrappage mandates.

Fuels and technologies keeping ICE relevant

Internal combustion is also evolving. Manufacturers and fuel suppliers are deploying efficiency upgrades and lower-carbon fuels that cut emissions while leveraging existing engines and infrastructure.

• Hybrids and plug-in hybrids: Atkinson/Miller-cycle engines, downsizing, turbocharging, and smart transmissions deliver major efficiency gains when paired with electrification.
• Advanced aftertreatment: Modern diesel SCR systems, diesel particulate filters, and gasoline particulate filters reduce local pollutants to stringent standards.
• Biofuels and renewable diesel: Ethanol blends (E10–E20), biodiesel, and hydrotreated vegetable oil (HVO/renewable diesel) lower lifecycle CO2 and are already used at scale in some fleets and regions.
• Gaseous fuels: CNG/LNG engines cut certain pollutants and can reduce CO2 compared with diesel; renewable natural gas can further improve lifecycle profiles.
• Hydrogen ICE: Engine makers are piloting hydrogen-combustion heavy-duty platforms that leverage familiar engine architectures while targeting lower CO2.
• Synthetic e-fuels: Early deployments and testing are underway, mainly for aviation and high-performance or legacy applications, though costs and supply are limiting today.

These pathways won’t eliminate tailpipe emissions entirely, but they can reduce the footprint of existing and new ICE assets during the transition, particularly in hard-to-electrify segments.

Outlook

The internal combustion engine is still very much in use today and will remain part of the global energy mix for years. However, its market share in new sales is declining in light-duty vehicles, and policy plus technology are steadily pushing more segments toward zero-emission options. The most persistent ICE strongholds will likely be long-haul trucking, aviation, maritime, and heavy off-road equipment—areas where energy density, refueling logistics, and duty cycles make rapid electrification more difficult.

Summary

Internal combustion engines remain widespread across transport and industry in 2025, powering most of the global vehicle fleet and many critical machines. EVs and hybrids are growing quickly, policy targets for new sales are tightening, and cleaner fuels and more efficient engines are narrowing ICE emissions. Even so, the installed base and performance needs in heavy-duty and specialized sectors ensure combustion engines will continue to operate—and matter—for decades, even as their share of new sales falls.

Are internal combustion engines still used?

Yes, internal combustion engines (ICEs) are still widely used across various sectors, including nearly all heavy-duty vehicles, heavy machinery, aviation, and marine applications, and will remain relevant for decades. While the adoption of electric vehicles (EVs) is growing, the infrastructure for widespread EV use is still developing, and ICEs offer benefits like power and durability, especially in niche applications. Furthermore, ongoing development aims to improve ICE technology and utilize lower-carbon renewable fuels, ensuring their continued role in reducing carbon emissions.
 
Sectors still using ICEs:

• Heavy-Duty Transportation: Over 99% of commercial vehicles, including large trucks, use internal combustion engines. 
• Heavy Machinery: ICEs are essential for power generation, agriculture, construction, and other heavy-duty, off-road applications. 
• Aviation: Many general aviation and private aircraft still rely on piston engines, a type of internal combustion engine. 
• Marine: Internal combustion engines, particularly diesel, are used in many marine applications. 
• Specialty Vehicles: Powerful and lightweight engines for motorsports, racing, and some motorcycles also continue to use internal combustion technology. 

Reasons for continued use:

• Infrastructure Limitations: The global infrastructure is not yet prepared for a full transition to electric power. 
• Durability and Power: ICEs provide outstanding durability and can still provide the power needed for demanding applications. 
• Alternative Fuels: ICE technology can be adapted to use lower-carbon, renewable fuels such as biodiesel, hydrogen, renewable natural gas, and e-fuels, helping to reduce emissions. 
• Ongoing Development: Automakers and other industries are continuing to develop new and improved internal combustion engines to meet efficiency and emissions standards. 

Are combustion engines coming back?

Can internal-combustion engines stay relevant in an EV world? (Hint: the answer is yes). The internal-combustion engine is far from dead, and motorsports and aftermarket performance companies will play a key role in making ICE vehicles environmentally sound for decades to come.

What replaced the internal combustion engine?

Another possible replacement for the internal combustion engine is an electric motor powered by hydrogen fuel cells. Such a fuel cell combines hydrogen and oxygen to create an electrical current to run the motor.

What states have banned internal combustion engines?

Seventeen states have historically followed California’s regulations, but so far only Delaware, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington have announced they’ll enforce the Advanced Clean Cars II rule and prohibit the sale of new gasoline-powered …