[Allch Chcar]

rmay635703, you are of course correct. It's been that way since the 50's? Dang. I wasn't trying to suggest that a Diesel gets worse efficiency even in a much larger engine than GASOLINE. My point was Diesel gets better fuel economy due to Diesel's energy content AND it's thermodynamic efficiency. If you have another fuel that gets the same thermodynamic efficiency but less energy per gallon the fuel with more energy is going to look much better in comparison.

My point was that with Ethanol you get the same energy efficiency as Diesel but you can keep a smaller Gasoline engine size without sacrificing HP or even keep a Diesel engine but run a different fuel, Diesels can run any of a number of fuels with enough modification. The biggest difference considering power and efficiency is Diesel has almost twice the energy content per gallon as Ethanol. So even though you're getting 20MPG on Diesel(just as an example) or BIODiesel, on Ethanol in a similar sized Diesel engine you would get closer to 10MPG.

But If Diesel gets you .89:1 Energy balance and Ethanol Gives you 1.3:1 which is really better? Ethanol can sell for $2something a gallon and Diesel here sells for almost $3 a gallon. Naturally it doesn't makes much sense to pay $4 to go the same distance as Diesel when you can run BioDiesel and pay even less or the same as PetroDiesel. So I don't think it really matters unless you have other goals in mind which fuel is better. Ethanol engines are cheaper up front than Diesel either way and with more undersized high compression turbo engines we could see some competition with Diesel in the Daily Driver market. Diesel just recently switched over to low-sulfur fuel and has been marketed more for the fuel economy minded. But watch for the day Diesel hits $4 a gallon. Even then Ethanol will still be $2 a gallon.

My whole argument here is that Ethanol is on par with Diesel for thermodynamic efficiency. The fuel efficiency is less due to energy content but you're not losing energy, just volume and weight. Ethanol is Renewable, Diesel is not. We're not discussing eliminating any fuel entirely, except some might argue for Ethanol's dissolution. I think there is a good enough argument for increasing Ethanol usage among vehicles.

Now with Biodiesel, I think this is a good thing recycling and gaining fuel from otherwise trashed vegetable oils. But it's even more resource restricted than Soybean Biodiesel. There have been reports of Ethanol/Diesel mixtures having positive effects on emissions. And Ethanol can be run in a higher compression Diesel engine or even used as an additive in regular Diesel. Enough to suggest that Soybean Biodiesel isn't necessarily the only route for renewable fuel or fuel additives in regards to Diesel. Diesel isn't going to be dismissed by Ethanol based fuel it can be embraced. Where weight is less of an issue such as commercial trucks and buses a Diesel powered vehicle is often the only way to efficiently transport people and products. Those vehicles can be run on Ethanol but once you switch fuels completely just like going Gasoline to Ethanol engine it's expensive switching back. Flexfuel Vehicles are the worse example of Ethanol power plants you can find. If you saw the benefits of alcohol based fuels I think you all would like the gains that can be made by providing at least one common sense alternative fuel.