The combustion engine has shaped mobility for more than 130 years. Its future role is being reassessed as technology develops and regulatory frameworks change.
Alongside battery-electric propulsion, renewable and synthetic fuels are also being discussed as possible technological options for the transport sector. This opens up new perspectives for existing propulsion systems.
Below, we consider current developments, technical approaches and the possible role of the combustion engine in a technology-neutral mobility system.
Environment and regulation: the major challenges
Assessing emissions separately
CO₂ and other greenhouse gases affect the climate. Nitrogen oxides and particulates, by contrast, are air pollutants. Comparing propulsion systems also requires consideration of production, energy supply, use and disposal. A single exhaust emission figure does not capture this overall balance.
Emissions and climate change
Burning carbon-containing fuels releases CO₂. Electric vehicles produce no exhaust emissions while driving; emissions from manufacturing and electricity supply nevertheless form part of their life cycle balance. Under its assumptions for Germany, the 2024 UBA study finds that battery-electric cars have a climate advantage over cars running on fossil fuels.
Source and assumptions: German Environment Agency, 2024 study.
Regulatory measures
The current EU fleet rules set CO₂ targets for new passenger cars and light commercial vehicles. They provide for a 100 per cent reduction in fleet emissions from 2035 compared with the 2021 target. Vehicles already registered must be considered separately.
The Commission proposed changes in December 2025; Member States are examining the proposal. Proposed flexibilities should therefore not be treated as rules already in force.
Source: Council of the European Union – current rules and proposed amendment (reviewed on 23 September 2026).
Innovations and technological advances
Increased efficiency
Modern combustion engines are significantly more efficient than their predecessors. Thanks to technologies such as direct injection, turbochargers and variable valve timing, fuel consumption has been significantly reduced. Hybrid drives combine combustion engines with electric motors to further increase efficiency and performance.
Exhaust gas aftertreatment
Advances in exhaust aftertreatment, for example through SCR catalytic converters and particulate filters, help reduce certain regulated pollutant emissions. These technologies enable compliance with applicable emission limits and reduce selected air pollutants during driving.
Alternative fuels
The development and introduction of alternative fuels such as eFuels, biofuels and Hydrotreated Vegetable Oils (HVO) open up new possibilities. These fuels can be produced using renewable energies and are compatible with existing engines and infrastructures.
The role of eFuels and synthetic fuels
The game changer for the combustion engine?
eFuels and synthetic fuels offer a promising opportunity to make combustion engines more climate-friendly and accelerate the decarbonisation of transport. They enable an immediate reduction in new CO2 emissions without having to wait for a complete transition to new vehicle technologies and infrastructure.
A technology-neutral approach that considers eFuels alongside electric mobility and other propulsion technologies can open up additional options for defossilising transport. Investment in research, infrastructure and suitable regulatory frameworks is crucial to further developing the technical and economic applications of eFuels.
New CO₂ emissions and the greenhouse gas balance
Here, “new CO₂ emissions” means CO₂ emissions added to the atmosphere through the use of fossil fuels. Burning carbon-containing eFuels also releases CO₂. Any potential reduction must be assessed over the entire life cycle against a specifically identified fossil reference fuel. The electricity and CO₂ sources, production, transport and use are particularly important. A CO₂ cycle alone does not demonstrate climate neutrality.
Japanese companies such as Toyota and Mitsubishi are already investing in researching and introducing eFuels as a possible technological option for defossilising transport.
Combustion engine vs. electric car: competition or complement?
Life cycle assessment
A robust comparison considers vehicle and battery manufacturing, energy or fuel supply, mileage and disposal. For eFuels, the sources of electricity and CO₂ are particularly important. This does not establish that their CO₂ balance is generally as good as, or better than, that of electric cars.
Under its scenario assumptions, the 2024 UBA analysis identifies a climate advantage for battery-electric cars. Any individual alternative fuel must be assessed on the basis of its verified supply chain.
Infrastructure and resources
Electric vehicles require charging points and adequate grid connections. eFuels that meet standards and have the relevant approvals can use parts of existing fuel logistics; however, producing them requires additional plants and renewable energy.
Batteries require different raw materials depending on their chemistry. eFuel plants, electrolysers and energy facilities also require materials. Raw material and environmental impacts therefore cannot be attributed categorically to one technology.
Areas of application according to technology
Battery-electric propulsion is used in urban traffic, on longer car journeys and increasingly in freight transport. Suitability and economic viability depend on the vehicle, operating profile and availability of charging.
eFuels are being discussed particularly for applications that are difficult to electrify directly and for suitable existing vehicles. Availability, price and energy demand limit their possible uses.
New CO₂ emissions and the greenhouse gas balance
Here, “new CO₂ emissions” means CO₂ emissions added to the atmosphere through the use of fossil fuels. Burning carbon-containing eFuels also releases CO₂. Any potential reduction must be assessed over the entire life cycle against a specifically identified fossil reference fuel. The electricity and CO₂ sources, production, transport and use are particularly important. A CO₂ cycle alone does not demonstrate climate neutrality.
Mobility for all: social justice through technological diversity
Electric vehicles often have higher purchase costs than vehicles with combustion engines. Used electric vehicles are currently available only in limited numbers, which can make access more difficult for some consumer groups. Operating existing vehicles on eFuels or renewable fuels can offer an additional mobility option and allow existing vehicle fleets to remain in use.
The automotive industry is an important sector of the economy, especially in countries such as Germany.
Maintaining and further developing the combustion engine can secure jobs and promote innovation.
Charging infrastructure for electric vehicles is often insufficient in rural areas. Renewable fuels can offer an additional mobility option there, as they can be used through existing fuel infrastructure.
Future scenarios: What will the mobility of tomorrow look like?
Scenario 1: Complete electromobility
Opportunities:
- Reduction of local emissions
- Promotion of renewable energies
Grenzen:
- Infrastructure requirements
- Dependence on raw materials
- High acquisition costs
Scenario 2:
Technology mix
Advantages:
- Utilizing the strengths of different technologies
- Flexibility
- Faster transition to climate neutrality
Implementation:
Combination of electric vehicles, eFuels, biofuels and hydrogen
Scenario 3: Continuation of the status quo
Risks: Failure to meet climate targets, environmental pollution, economic disadvantages due to innovation backlog.
Internal combustion engine:
Farewell or a new beginning?
The combustion engine has played a major role in shaping mobility over recent decades. Several technological pathways are available to meet the need to reduce greenhouse gas emissions. These include battery-electric propulsion, hydrogen applications and renewable fuels such as eFuels. A technology-neutral approach can consider different propulsion systems and energy carriers, thereby identifying additional options for defossilising transport. Alongside technical aspects, social and economic conditions can also be taken into account.
Mobility is likely to be shaped by a range of technologies in future. A technology-neutral approach allows different propulsion systems and energy carriers to be used according to the application. In combination with renewable fuels such as eFuels and other technological options, the combustion engine can provide a possible complement within a diverse mobility mix.
The question is not whether the combustion engine has had its day, but how we can integrate it into the mobility of tomorrow through innovation and responsibility.
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