With some fanatical followers of VW’s diesel engines with gas mileage around 50 miles per Gallon, the question is frequently asked, why not a hybrid and get 100 miles per gallon?
There are a couple of drawbacks that keep this from being a no-brainer. The first drawback is price. The cost to manufacturer a diesel engine is about 15% higher than a standard gas engine with similar output specs. The other problem in the American market is that gas is just too cheap. The economics makes sense more so in Europe when the gas price was flirting with $10 per gallon. The gas in the United States is hovering t $2 per gallon.
There becomes a law of diminishing returns. If the cost to manufacturer is significantly more and the price of gas is so cheap, what are the economics that make this a wise investment. You can play on the culturally aware, eco-friendly card. But like Solar Electricity has been, the benefit is not justified by the cost.
Another factor is determining whether the diesel and electric motors are on the same powertrain or separate powertrains. Only Mercedes has a version on the same powertrain. The Peugot and Citreon have separate powertrains. this allows the electric to handle the load at lower speeds, while diesel takes over at the higher speed. All of these cars are available in Europe, again because the price of gas is dramatically different then the price of gas in the United States.
The market will ultimately tell us whether diesel hybrids can be financially justified. The markets will also be dictated by the cost of gas in any given country at any given time. World events and a disruption in gas supply could change the calculus, but right now the investment does not seem to make sense for diesel hybrids to be sold in mass in the US.