We are seeing increasing resistance against diesel cars in cities, because they pollute the air right where people want to live, with soot and NOx that can cause heart and brain damage. In the defence of the car companies we read that they say diesel engines are more efficient, get more miles per gallon. It’s an interesting claim because it shows you how these interests will hide reality from you even in small portions. They are never honest.
The truth is, diesel is more energy dense than gasoline, so one gallon of diesel contains more energy than one gallon of gasoline. So it’s natural you get more miles out of a diesel engine using the same volume of fuel. That said, a diesel engine is slightly more efficient because it is hotter, diesel doesn’t ignite as easy so it needs to be. Hotter also means you can extract more energy because the temperature gradient limits the amount of work you can get out of a heat engine (which an internal combustion engine ultimately is). So technically yes, a diesel engine makes better use of the energy avialable, but you don’t show that by comparing miles per gallon.
But the overal efficiency of an internal combustion enigine is appaling. 30% maximum. So 2/3 of all the emissions from cars trucks ships, planes (who are probably worse) is just wasted buring of fossil fuels.
To me that should be reflected in the price, the energy in the fuel. So if I buy a gallon of diesel, it should cost more than one of gasoline. The cheapest form of energy should be used as a base price, and that isn’t diesel or gasoline. It is solar, because no oil well or gass well stops needing attention, a solar panel does. The cost of a solar kWh should be the standard for all energy carriers, so that we price gasoline correctly (source).
Say a solar kWh = $0.10 ct.
A gallon of gasoline should cost $3.34
and diesel $3.79
Another sane thing is to tax in engine efficiency to incentivise more efficient use of energy. So for an EV with an electric motor, efficiency is about 85%, so you divide the cost by this efficiency, you get $0.117 ct/kWh. For gasoline and diesel this translates to
Gasoline $3.34 /0.2 = $16.7 Gallon
Diesel $3.79 /0.3 = $12.6 /Gallon
Another way is to price the roadmeters into the fuel, for transportation fuels. This means you include the average engine efficiency and take the optimal performance as the benchmark.
The average EV gets 0.32 kWh per mile. This is probably a low estimate as Tesla’s do better than this.
A gasoline car gets 23 miles per gallon, which is 23 miles/33 kWh = .69 kWh per mile
So a gasoline car should pay twice as much as an EV per mile.
In order to control congestion you could introduce a system whereby you set prices such that the minimum of traffic jams happen, then you will have to increase the cost of road kWh considerably, and as a consequence the price of road gasoline and diesel. Instead of maximizing for fuel consumption as our current economy does, one could maximize for efficiency in the road system, which clearly has not been an objective. This way fossil fuel companies can no longer dominate the transportation market by dumping their energy at the lowest possible cost.