I suppose diesel is a good thing if newer "green" cars are using it.
Diesel models have recently been bumped into the spotlight as “green” for a few reasons. Diesel engines are inherently more fuel efficient than standard gas engines, plus the use of new clean-diesel fuel has significantly improved diesel emissions.
The difference between cars that use diesel compared to gasoline isn’t just the fuel itself. A diesel engine is specifically designed to run on diesel and is built differently than a standard gasoline engine.
Both engines work on the basic principle that fuel needs to be burned to create power. Diesel fuel is more resistant to combustion and a diesel engine depends on higher engine compression — which creates heat — to burn the fuel, instead of a spark like in gasoline engines. That higher compression as well as the increased energy content of diesel fuel contributes to better fuel efficiency compared to gasoline engines.
The stigma that diesel needed to overcome was the image of big-rig syndrome. People still associate diesels as noisy and dirty engines that puke out huge clouds of black smoke. The truth is that newer diesel engines don’t have those traits at all.
From the Cars.com Green Buying Guide Article, “The Return of the Diesel”:
“The most important point is that diesels are no longer dirty, stinky or noisy, thanks to new clean-diesel technology expected to hit our streets by the end of this year. They're pretty much as clean as gas engines. What makes them greener is that diesels are about 30 percent more efficient than gas engines of comparable performance. If you're burning 30 percent less fuel, that means 30 percent less carbon dioxide — a greenhouse gas — produced, which is what typical hybrids deliver. Voila! Suddenly diesels are green.”
Learn more
Red, you're right on. A 42 gallon barrel of crude oil is required to produce 7 gallons of diesel. A 42 gallon barrel of crude will yield 20 gallons of gasoline. Diesel fuel is 20-40% more efficient than gasoline. Why is there such a desire to use twice as much crude oil to produce a diesel quantity that does not equal one barrel of crude for gasoline? 20 gallons of gasoline at 30mpg = 600 miles (one barrel of crude required). 14 gallons of diesel at 40mpg = 560 miles (2 barrels crude required).Go figure!
You two are looking at it wrong.
The refinery turns 42 gallons of crude into 42 gallons of assorted petrochemicals. The refinery is turning 1 barrel of crude into 20 gallons of gas AND 7 gallons of diesel. The same way a dairy can split a gallon of whole milk into skim milk and cream.
does that really matter? for about $100, you can get any diesel car retrofitted to run on biodiesel, i.e used vegetable oil.
not only is it clean, but it smells like french fries coming out of the tail pipe.
AV, you raise a good point. If we can produce enough biodiesel, and then have cars designed to run on it, that would help greatly. Unfortunately, the new "clean diesel" cars coming out will only allow five percent biodiesel to be mixed with regular diesel fuel. Any higher percentage and the manufacturers will void the warranty. That leaves diesel car owners of the future competing with truckers for nearly all their fuel, and neither camp will be happy with the price they'll be paying. GrapeApe, I understand your point, but I'm not sure that refining crude oil is a matter of choosing what you want - according to the link above, it actually takes more crude to produce diesel fuel - it's not a one to one proposition to get a gallon, if I'm reading it right. When comparing diesel fuel to gasoline you have to reduce diesel's mpg figure by about 20 percent to get a true picture of how efficient each fuel is compared to how much crude it took to produce it. Europe has 40 percent diesel cars because their governments put on tax incentives to promote diesel. We didn't, and it never took off for our cars here. If you ask me, that was a lucky break.
How much diesel or gasoline you get from a barrel of oil depends on the process used in your refinery. Catalytic cracking, which is the primary process used in the US, produces alot of gasoline from a quantity of oil, and a relatively small ammount of diesel. I saw a good article on this lately but, of course, I can't find it now. Hydrocracking produces more diesel fuel and less gasoline, and is the primary process used in the rest of the world, particularly Europe and India. The rest of the barrel of oil isn't thrown out though, you just get other products like kerosene or plastic.
So to say that diesel takes more oil isn't really accurate, but you do get less diesel from a barrel of oil than you do gasoline. That, of course, assumes you're using catalytic cracking in your refinery. Changing a refinery over to a new standard is no small task though. And using a different type of crude such has heavy sour instead of light sweet can change the optimal refining method and end products as well.
So, if we wanted to produce more diesel we could convert over our refineries, but it would be an expensive process, and would reduce the gasoline supply. That would raise gasoline prices in order to cut diesel prices, but if the demand for diesel shoots up, that would be prudent.
I don't think the question was answered. As I see it - the question was what is the difference ebtween gasoline fuel versus diesel fuel. I wondor the same thing.....
I thought I posted a link that explains what is the difference between gasoline and diesel (as well as kerosene). It could be found on howstuffworks.com
Perhaps a better way to normalize the comparison. A barrel of crude has a certain energy content that is preserved in the refined output.
Diesel fuel is denser than gasoline (0.85kg/l compared with 0.72kg/l) and so despite having less energy content on a per weight basis (45.3MJ/kg vs. 45.8MJ/kg) ends up having 15% more energy on a per fluid volume basis.
This somewhat accounts for the greater mileage per unit volume for Diesel, reducing the actual mileage advantage from engine efficiency to about 20% (the rest coming from the fuel simply containing more energy).
Given that the energy densities are relatively similar, it doesn't make sense that the 20 gallons gasoline & 7 gallons Diesel from a barrel of crude is due to some sort of waste in the Diesel process. Obviously, both fuels are receiving a similar share of the energy content of the original crude and are simply being made in different quantities.
It's also worth noting that CO2 output is less on a per mile basis with Diesel. The argument that this is more than compensated by particulate emission is true to many engines, but several upcoming engines (such as VW's TDI to be used in the Jetta this summer) will trap these particulates and then recycle them by burning them periodically. Then net is still lower CO2 and very low particulates. This new exhaust system isn't cheap, unfortunately, which is why VW is introducing it in the Jetta and not the higher-volume Golf/Rabbit model (they feel the market for the cheaper model wouldn't tolerate the cost bump ... at least not in the US market).
The French allready use DTI diesel engines in great numbers and they work great. I own a DTI renault kangou and it gets similar milage or slightly less than my hybrid. The renault Cleo is has efficient as a hybrid. I can wait for the hybrid diesel to arrive on the US market. DTI diesel bits gasoline engine hands down.
See if your question has already been asked and answered
Your question has been successfully submitted to Ask.cars.com. It will now be reviewed by our editors and we'll answer it soon if we think it's a useful question. You will be notified via e-mail when the answer is posted. Ask.cars.com tackles your questions about new cars and the car-buying process. Unfortunately we can't answer questions regarding:
Have our experts answer any of your questions about new cars.
Don't worry — we won't publish your last name or email.
I know automotive diesel engines are better than the disasters of the past, but they are far from clean. I was behind a V10 Tourareg today (a 15 mpg diesel guzzler)and the exhaust finishers had oil deposits all over them and the rear bumper was discolored from the diesel fumes.
If we put more diesel cars on the road, the price of diesel fuel will skyrocket because there's only so much of it made by our refineries. It takes 25 percent more oil to produce a gallon of diesel fuel compared to gasoline so I don't see the price ever going below the cost of gas, so there goes the money savings from the decent diesel mpg. Our over the road truckers are already being hurt by high diesel prices, and that's raising the price of everything they haul for everyone. The Black Carbon emitted from diesel engines is a huge contributor to global warming and the fine particulate pollution from the fuel is a major health threat. To top it off, Diesel is only available at 10 percent of American service stations. Let's leave the diesel fuel to the professionals who need it for their big rigs and focus on gasoline hybrid cars. The following link has interesting information on diesel fuel vs. gas:
http://www.grinningplanet.com/2005/04-12/diesel-vs-gasoline-article.htm