The Log
14 June 2025: The Technology Guide paper on SCR Systems for Diesel Engines has been updated with additional coverage of the SCR-on-filter technology and other edits.
12 June 2025: A summary of the technical sessions from the 31st CIMAC World Congress held in Zurich, Switzerland on May 19-23, 2025 [more ...]
9 June 2025: The US National Highway Traffic Safety Administration (NHTSA) published an interpretive rule stating that the Biden administration ignored statutory requirements when adopting the current CAFE standards. While the rule does not change existing CAFE or medium- and heavy-duty fuel economy standards, it sets the regulatory framework for the rulemaking process for replacement standards [more ...]
31 May 2025: A summary of the technical sessions from the 46th International Vienna Motor Symposium held May 14-16, 2025 [more ...]
26 May 2025: The US Senate has voted to revoke the waivers of preemption issued by the US EPA for three California emission regulations, including the Advanced Clean Cars II (ACC II), the Advanced Clean Trucks (ACT), and the Heavy-Duty Low NOx Omnibus Regulation, setting the stage for a legal battle between California and the federal administration [more ...]
17 May 2025: Updated Technology Guide paper on Powertrain Alternatives—added new section on the effectiveness of battery material use in electrified powertrains and some new discussion of life cycle emissions from hybrid vehicles.
13 May 2025: The US Department of Energy announced its “largest deregulatory effort in history,” proposing the elimination of 47 energy-related regulations [more ...]
8 May 2025: The European Parliament adopted flexibility measures for car manufacturers to comply with the 2025-2027 CO2 emission targets, as proposed by the Commission. To enter into force, the draft law now requires formal approval by the Council, which already endorsed the text.
7 May 2025: The updated Technology Guide paper on Diesel Spray Formation and Mixing includes more material on the Sandia’s ducted fuel injection technology.
1 May 2025: Tony Blair, the former UK Prime Minister, has called for a reset of climate policies. “People know that the current state of debate over climate change is riven with irrationality,” said Tony Blair in a report published by the Tony Blair Institute (pdf version). In developed countries, the promised green jobs and economic growth have failed to materialize and “voters feel they’re being asked to make financial sacrifices and changes in lifestyle when they know that their impact on global emissions is minimal.” As a result, any strategy based on phasing out fossil fuels in the short term or limiting consumption is a strategy “doomed to fail.” While the report does not reject net-zero targets, it states that the current decarbonization policies are not working.
28 April 2025: A summary of the technical sessions from the SAE WCX 2025 Congress held on April 8-10 in Detroit [more ...]
24 April 2025: The Technology Guide paper on Alternative Combustion Engines has been updated with more material on split-cycle engines and several other edits.
16 April 2025: The IMO’s Marine Environment Protection Committee (MEPC) approved draft mid-term GHG measures that would regulate the GHG intensity of fuel used by ships using economic instruments [more ...]
7 April 2025: A new Technology Guide paper, Non-Exhaust Particle Emissions, discusses particle emissions from brake and tire wear.
4 April 2025: The CIMAC Congress Technical Program is now available online. The program includes 207 full presentations and 44 posters by authors from 23 countries. The 31st CIMAC Congress will take place on May 19-22, 2025 in Zurich, Switzerland.
26 March 2025: US President Trump has placed a 25% tariff on all foreign-made cars imported into the United States [more ...]
25 March 2025: This year, the SAE Energy & Propulsion Conference and the Thermal Management Systems Symposium are co-located—both events open on October 14, 2025 in Ypsilanti, Michigan. The events offer full access to current research and dynamic discussions on electrification, fuel efficiency, zero emissions, and thermal challenges in electric vehicles. You can also share your latest research and edge-case studies for advancements in propulsion, powertrain, emissions, fuels and batteries—the calls for papers and presentations for both events are still open. Don’t miss this chance to engage with top minds from across the industry!
24 March 2025: Global energy demand grew at a faster-than-average pace in 2024 as the consumption of electricity rose around the world—with increased supply of renewables and natural gas covering the majority of additional energy needs, according to the IEA’s Global Energy Review [more ...]
18 March 2025: Register now for SAE International’s annual COMVEC™, returning to Schaumburg, Illinois, on September 16-18, 2025. This industry leading event brings commercial vehicle professionals in the on-highway, off-highway and defense sectors together to collaborate in a neutral environment on what’s new in commercial vehicles—including trends, tech, evolving standards and regulations, and smart strategies. Make plans to attend!
13 March 2025: The US EPA has announced ‘historic’ actions to roll back air emissions regulations for vehicles and the energy sector. Among vehicle regulations, the EPA will reevaluate MY 2027 and later GHG emission standards for light-duty vehicles, Phase 3 GHG emission standards for heavy-duty vehicles, as well as the 2027 NOx emission standards for heavy-duty engines and vehicles [more ...]
11 March 2025: Only seven countries met the WHO air quality standards last year, according to the World Air Quality Report by Swiss air quality firm IQAir. The countries that met the WHO annual average PM2.5 guideline of 5 µg/m3 are Australia, Bahamas, Barbados, Estonia, Grenada, Iceland, and New Zealand. Byrnihat, India was the most polluted metropolitan area of 2024, with an annual average PM2.5 concentration of 128.2 µg/m3. The region of Central & South Asia was home to the top seven most polluted cities in the world. India was home to six of the nine most polluted global cities. Oceania is the world’s cleanest region, with 57% of regional cities meeting the WHO PM2.5 annual guideline.
7 March 2025: Cummins announced two new medium-duty B Series engines: the B7.2 diesel engine and the B6.7 Octane gasoline engine—Cummins’ first advancement into the gasoline market. The gasoline engine, while somewhat less powerful than diesel, avoids costly DPF/SCR aftertreatment, avoids DEF, and makes 2027 emission compliance much easier [more ...]
Engines & Emissions | Our Credo
The internal combustion engine (ICE) has been a key prime mover that largely replaced earlier prime movers of lesser efficiency—human labor, animal work, the water wheel, the windmill, and the steam engine—thus enabling modern industrial civilization. The most efficient type of ICE, the diesel engine, has been widely used in heavy trucks, construction and agricultural machinery, rail locomotives, ships, and emergency power generation. Its gasoline counterpart has been common in passenger cars. Another related power plant, the gas turbine, has been powering commercial aviation.
For many years, engine developers have been striving to make engines cleaner. Following the three-way catalyst for gasoline engines, clean diesel technologies that enabled near-zero emissions of PM and NOx were developed and introduced in many regions of the world. The focus in technology development has then shifted to climate change and energy efficiency. The benefit of low CO2 emissions, traditionally associated with the diesel engine, is no longer sufficient to meet GHG and fuel economy regulations. New technologies are being developed—such as new combustion techniques, powertrain electrification, and waste heat recovery—that further increase the efficiency not only of the engine itself, but of the entire vehicle. Critically, as GHG emissions occur at all stages of vehicle life, from manufacture through disposal, low-carbon policies must consider life cycle effects of fuels and vehicles.
A major challenge ahead is the approaching end of the Oil Age—not only due to climate policies, but for economic reasons stemming from the depletion of easily recoverable oil resources. As fossil fuels are replaced by alternatives of lesser energetic quality, the future of mobility remains largely unknown. While the world aims to embrace more sustainable mobility, most alternative powertrain technologies depend on quantities of rare and nonrenewable natural resources, and therefore are not truly sustainable. Another often suggested approach—that of fueling the ICE by low-carbon e-fuels—suffers from low efficiency and would require substantial amounts of energy, which seems problematic in an economy that no longer has access to cheap and abundant fossil energy. All this suggests that future mobility will be based on a mix of powertrain technologies, where combustion engines continue to play an important role.