Over the past few decades, the automotive industry has been investing in and accelerating improvements of vehicles’ performance, especially the fuel consumption and emissions of internal combustion engine (ICE) vehicles. With the global focus on climate change, and the mobility industry serving as a major contributor of emissions responsible for climate change, major questions linger — Has the automotive industry been responsible and aggressive enough in adapting ICE vehicles to support this global focus? Do technological advances of ICE vehicles warrant their continued existence? Should ICE vehicles be phased out or be continued?
Datasets
To address the white elephant in the room, the dataset providing detailed information of all ICE passenger vehicle models in the United States (US) between 2000 and 2022 was evaluated. This dataset contains details of every ICE passenger vehicle model in the US, including vehicle type (sports utility vehicle (SUV), car, etc.), emissions, fuel consumption, make, engine size, number of cylinders, transmission type, and fuel type.
To identify any correlation between the global temperatures and the performance of ICE vehicles, another dataset providing changes in global annual mean temperatures between 1880 and 2022 was selected.
Since the US is one of the primary users and innovation hubs of the automotive industry, we focused on car emissions of the US-based car models to generalize global trends.
ICE passenger vehicle models reduced since 2018
The total number of ICE passenger vehicle models increased between 2000 and 2010, remained about the same between 2010 and 2018, and tapered post 2018. The initial increase in the number of models could be due to the booming automotive industry and to account for the varied interests of millennials.
The number of regular vehicle models have remained similar since 2003. The number of luxury vehicle models have increased consistently during the last two decades. This increase in luxury models could be due to increased affordability of consumers in the US, changing landscape in the automotive industry to compete with newer technology vehicles such as those from Tesla, etc.
Average fuel consumption of ICE passenger vehicles has remained similar since 2000!
It is surprising that despite technological improvements, the combined average fuel consumption of ICE passenger vehicles has remained similar in the last two decades, at about 11 liters per 100 km (L/100km)! The combined average fuel consumption dropped by about a liter per 100 km between 2000 and 2014 (possibly due to technological innovations). However, since 2014, this value increased back by about the same amount. This recent uptrend could be due to increased weight of cars from the increasing number of gadgets, such as in-built GPS units, advanced driving assistance systems; increasing proportion of luxury-to-regular car models; increasing SUV and truck models; etc.
Between 2000 and 2022, variations in average fuel consumption of ICE passenger vehicles remained similar for city- and highway-based driving. In recent years (since 2015), the average fuel consumption of these vehicles improved nominally for city-based driving (remained at about 12.5 L/100 km) and minimally for highway-based driving (increased from about 9 to 9.5 L/100 km).
Average emissions from current and year 2000 ICE models are similar!
There is a strong correlation between average fuel consumption and average emissions of ICE passenger vehicles. Similar to combined average fuel consumption, average emissions of ICE passenger models dropped between 2000 and 2014 and increased since 2014. It is surprising that average emissions from the current ICE passenger models are similar to those from year 2000 models, about 260 grams per mile (g/mi)!
Models with higher emissions are on the rise!
The most common fuel types for ICE passenger vehicles now-a-days are Regular and Premium Gasolines, with similar number of models for each fuel type. In recent years (since 2018), Regular Gasoline has the least average emissions at about 230 g/mi, with emissions from Premium Gasoline about 15% higher. The number of ICE passenger models using Premium Gasoline has been increasing during the last two decades. Manufacturing more number of models using Premium Gasoline is certainly not helping to minimize the overall emissions from ICE vehicles.
The number of cylinders in an ICE vehicle has a direct relationship to its emissions — the lower the number of cylinders, the lower the emissions and vice versa. At the turn of the millennium, most ICE passenger models had 6-cylinder engines. However, this trend changed last decade; currently, 4-cylinder engine models have the major share followed by 6-cylinder engine models. Since average emissions from a 4-cylinder engine are lower than that from a 6-cylinder engine, manufacturing more 4-cylinder models is beneficial to the environment from the emissions standpoint.
No substantial improvements to average car emissions since 2000!
Average car emissions have not substantial improved over the last 2 decades.
Luxury Category — Emissions associated with most luxury brands have either remained flat or increased! Lexus seems to have made some improvements in reducing emissions, while Volvo, Acura, and Alfa Romeo are the only original equipment manufacturers (OEMs) that have consistently hovered around the lower end of the emissions’ spectrum throughout the last 20 years.
Regular Category — 2009 to 2014 was the golden period when most car companies minimized average emissions from their models. Average emissions have increased since then for most brands. However, Hyundai, Kia, Honda, Mitsubishi, and Toyota appear to making progress over the last five years to lower emissions again.
Which is the greenest luxury ICE brand in the US?
The greenest OEMs manufacturing luxury cars in the US are Volvo and Lexus. Volvo, followed by Lexus have the least average emissions of all the luxury car brands in 2022, at about 225 g/mi! These two brands have the highest average mileage too in 2022, at about 30 mpg. Bugatti, Lamborghini, and Rolls Royce are the worst luxury car brands from average emissions and mileage standpoint.
Which is the overall greenest ICE brand in the US?
Regular cars are performing better then luxury cars in terms of average emissions and fuel mileage. Hyundai, followed by Honda and Mini have the least average emissions of all the regular car brands in 2022, at about 175 g/mi. Hyundai, followed by Kia, Honda, and Toyota have the highest average mileage in 2022, at 35+ mpg. The greenest passenger vehicle OEM (manufacturing luxury or regular cars) in the US is Hyundai, followed by Kia, Honda, and Toyota. While, GMC, Dodge, Ram, and Chevrolet are the worst brands, in terms of average emissions and fuel mileage, manufacturing regular passenger vehicles in the US.
Is there a correlation between ICE vehicle emissions and earth’s temperature?
Average emissions from ICE passenger vehicles reduced between 2000 and 2014 by about 13% (from 260 to 225 g/mi approximately ) and increased back to about 260 g/mi by 2022! During that 22-year period, average surface temperature of earth has consistently risen! Currently, its average surface temperature is about 0.9 °C higher than the long-term stable value during the 1950–80 period! Since 2021, the average surface temperature of earth has shown a downtrend, possibly due to Covid-19 pandemic related reduction in travel and emissions.
It is noteworthy that around 2015, average emissions of ICE passenger models spiked by about 30 g/mi, and the earth’s average surface temperature soared by about 0.25 °C. Clearly, the inconsequential decrease in ICE passenger vehicle emissions between 2000 and 2014, followed by their increase in the most recent 8 years has not helped to lower or stabilize the earth’s surface temperature.
Final thoughts
Our lovely planet has been heating up! Since 1980, it’s average surface temperature has risen by about 0.9 °C! At the Paris Agreement in 2015, the global treaty on climate change, countries pledged to limit the increase in average surface temperature of earth to under 1.5 °C. This is a key metric, and we are dangerously inching towards that target every year.
Climate change is a complex science, with many intricate dependencies and interdependencies. It’s hard to narrow down on one causal factor. However, it’s an established fact that transportation, especially fossil fuel based vehicles, is a major contributor of climate change. This fact has been re-confirmed by the decrease in earth’s surface temperature since 2021, when Covid-19 pandemic reduced travel, and related emissions, globally.
To counter the negative environmental impacts and reduce emissions, automotive industry has been pioneering technologically. Despite all the technological and engineering advancements, the average emissions of ICE passenger vehicles operating in the US have remained similar over the last two decades, and earth’s surface has been consistently heating up due to greenhouse gas (GHG) emissions!
To stabilize, and possibly reverse, earth’s surface temperature and climate change effects, either tremendous advancements in ICE vehicle technology have to happen at an unforeseen rapid pace or we have to phase out fossil fuel based vehicles. The fact that ICE passenger vehicle’s average emissions remained similar over the last two decades does not lend confidence and credence that we, as a society, can aggressively and rapidly advance technologies to decrease emissions from fossil fuel vehicles. Ergo, for the continued livability of our beloved blue planet and to provide a sustainable abode for future generations, it is sane and imminent for us to focus on non-fossil-fuel based transportation and phase out ICE vehicles immediately.