The sulphur causes numerous problems with newer diesels. The biggest is catalyst poisoning. In a lean environment, sulphur compounds contaminate the catalyst rendering it useless. A gasoline engine runs at a stoichiometric air-fuel ratio (controlled to an average accuracy of about 0.001%) and the catalyst lasts a long time.
VW stopped selling diesels in the US primarily because the high sulphur diesel sold in the US (at the time) would have damaged the catalyst. Also, the US EPA penalizes nitrogen oxide emissions more than anywhere else in the world. I am of the opinion that the EPA rules have done a lot to prevent fuel consumption improvements. In most parts of the world, CO2 is a regulated vehicle emission, so the vehicle manufacturer can optimize NOx vs. CO vs. CO2 formation. They are a 'triangle' and you get to pick which side of the triangle you are on. The ultra-low NOx standards means that you need to be on the other side of the triangle, and if you're not making CO to zap the NOx in the catalyst, then you have to make a lot of CO2. You do that by making the engine larger and loading it lighter. Also, truck standards are quite a bit higher than car standards, so you see a lot of diesel trucks but not so many passenger cars.
The published fuel economy is measured not using real-world driving, but a very specific test cycle which was basically a strip-chart recording of someone's trip in LA, I think it was somewhere around 1970. The cycle was revised in 1975 to include a hot restart (the hot-505 portion of the test). It is a very relaxed drive, where even the most underpowered car (the Chevy Sprint) has no problem meeting the trace while almost always under 40% throttle, with the exception of about four seconds of the test (located at 180 seconds into the test), where the throttle would go to maybe 70%.
The rated fuel economy usually has little to do with what a driver gets except in comparing apples to apples. The actual number comes from measuring the CO2+CO+HC emissions of the vehicle and then calculating the fuel used, on both a highway driving cycle, and the US FTP-75 drive cycle.
Biofuels from crops (soybeans or whatever) usually forget a very important factor - the amount of petroleum products that go into growing the stuff. Fertilizer is made from natural gas, tractors run on diesel, pesticides are made primarily from petroleum. The ratio of produced fuel to petroleum inputs is only slightlt better than 1:1. This, to me, makes absolutely no sense. If biofuels are to make sense, we need to do them without the staggering oil inputs used in modern agriculture. Perhaps the algae method, or something like that? I dunno.
As for the price of fuel.... it is a product that is priced just like a cut of meat at a grocery store. In a free-market economy, what is wrong with an oil company deciding that fuel is worth $10.00 per gallon? All of the sudden there are congressional committees looking at it and everything. If the people are willing to pay $10.00 per gallon (while complaining about it), then why are the oil companies *not* charging that? As a shareholder in an oil company, I want to know why they are not getting all of the profit that they can so I can get dividends.
-Dale
