In 2012, 48.2 % of all cars sold in Germany were diesel powered. In January 2013, this market share rose to 50.2%. This trend leads one to believe that by next week or so every passenger car in Germany will have a diesel engine. Why shouldn't they? I know that Jalopnik is all about manual diesel wagons, but there are serious reasons that make me believe that the era of the diesel engine in cars might be coming to an end.

Fuel efficiency: Five years ago, diesel engines were 30% more efficient than petrol engines. Today, it's only 20-25% a number that will probably have shrunk to 15-20%  by 2020. Diesel engines have seen some serious development and refinement over the years, therefore further improvement will only come at tremendous cost, whereas petrol engines still have a lot of untapped potential.

Cost: Modern diesel engines are twice as expensive to built than their petrol counterparts, making a diesel powered Golf  € 2K more expensive than the petrol version. With upcoming changes in emissions legislation, this number will probably rise by another 1K. Unfortunatly, these expensive systems used to clean exhaust gases like particle filters and urea injection tend to have the unfortunate side effect of lowering fuel efficiency.

Fuel price: In Germany, the tax on diesel is lower than that on petrol, making diesel the cheaper fuel at the pumps. This has already lead to severe criticism by other EU nations (interference with the free market etc.). So it's quite likely that there'll be an end to this price difference sooner or later.

The maths: All the factors mentioned above, will push the annual mileage needed to just break even with a diesel car higher and higher, giving less people a reason to buy a diesel. As of now, the diesel has never quite caught on with small city cars, the future might see diesel engines only in luxo-barges and rep-mobiles. 

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The global market. In Europe, diesel engines in passernger cars are just the thing right now, but pretty much only in Europe. In other important markets like the USA or China, diesel only plays a negligible role. The question is, whether manufacturers can afford to further put money into a local concept or if they should rather invest that money in development for the global market.

With petrol engines getting more and more fuel efficient right now (ecoboost and so on), and still having a lot of potential (self igniting petrol engines might be 30% more efficient), the diesel engine might be at it's peak in terms of market share right at this moment in time. Will we, in 10 years time, see the diesel engine in non-commercial vehicles as a failed/failing concept, or not? Any opinions?