The Log
10 July 2025: The Technology Guide paper on Hydrogen Fueled Engines has been updated with several examples of recent hydrogen engine developments.
4 July 2025: A group of more than 600 of current and retired employees of the US Environmental Protection Agency (EPA) published a letter to EPA Administrator Lee Zeldin, saying the Trump White House’s efforts “undermine the EPA mission of protecting human health and the environment.” In response, the EPA has placed 144 staffers on administrative leave as it investigates the letter, The Hill reported.
26 June 2025: The Energy Institute released the 74th edition of the Statistical Review of World Energy (previously published by BP) presenting global energy data for 2024 [more ...]
24 June 2025: The updated Technology Guide paper on Hybrid Vehicles includes a new section on commercial applications of hybrid technology in light-duty vehicles.
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.
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.