As an engineer I have a visceral hatred for all those things that are inefficient, so heat engines for me, are among the most hated things. Let's start as a starting point that throughout the universe energy is finite, not created and not destroyed but transformed.

Great, so the reason why heat engines were invented is to take the energy contained in fuels such as gasoline and diesel, turn it into mechanical energy to perform a certain task. As Carnot teaches the maximum possible efficiency of any heat engine has a defined limit of less than 1, not only that but as the Otto cycle teaches this efficiency is as high as 30 percent.

So the mechanical energy we are able to extract from gasoline and use as mechanical energy to move is one third, the $100 of gasoline those we use is $30 the rest wasted in heat and exhaust, so if the efficiency is so low why do we still use heat engines? Because our luck (or misfortune) is that gasoline has a very high energy density (1 kg of gasoline has an energy density of 46.9 MJ, 1 banana has an energy of 397kJ), so even if the efficiency anyway is bad overall we thermal car owners are not affected.

Then as if the enormous waste of energy was not enough, let us remember that the heat engine produces exhaust fumes, let us remember the funny effects of leaded gasoline on our brains and our health, it has been estimated that about 412,000 people die each year in the U.S. from diseases associated with prolonged lead exposure over a lifetime. Instead, according to a study compiled by Michael McFarland, associate professor of sociology at Florida State University and a faculty member of the university's Center for Demography and Population Health. lead exposure made people born in the 60s and 70s dumber. But fortunately as of 2020, after nearly a century of use this lead-additive gasoline has been banned worldwide. Remember that road transport, accounts for 23.4 percent of total CO2 emissions. In addition to CO2, exhaust gases contain Carbon Monoxide (CO), Unfired Hydrocarbons (HC), Nitrogen Oxides (NOx), Sulfur Oxides (SOx) and Carbonaceous Particulate Matter (PMx). So when we walk quietly through our cities, let us remember that the:

-CO, binds firmly to the iron ion in the hemoglobin of the blood prevents oxygen from reaching the tissues.

-Uncombusted hydrocarbons (HC), some of these hydrocarbon-based compounds are carcinogenic.

-Sulfur oxides, exposure to these substances results in persistent coughing and irritation of the mucous membranes of the airways.

-Carbon particulates (PMx), result in acute and chronic respiratory (including cancers) and cardiovascular diseases.

In conclusion, if we have gone from riding horses to riding automobiles, I believe we will be able to abandon these heaps of crackling cast iron in favor of choices that are more ecological and less harmful to the environment and ourselves.