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[haven]

Over on Edmunds Inside Line web site, they report monthly on the mpg of their test cars. For March, a 2009 Volkswagen Jetta TDI with 2.0L diesel engine averaged 35.6 mpg, with one tankful recording a best mpg of 43.0 and worst tankful at 28.7 mpg. The EPA rates the Jetta diesel at 34 mpg in combined driving, so Edmunds is doing a little better than the EPA predicted.

For USA nationally, diesel fuel is about 23 cents per gallon (8%) more expensive than regular gas. That difference drops to 15 cents in the Midwest, and only 7 cents more expensive than gas in many parts of the West.

Chip Haven

 

[EMrider]

Over on Edmunds Inside Line web site, they report monthly on the mpg of their test cars. For March, a 2009 Volkswagen Jetta TDI with 2.0L diesel engine averaged 35.6 mpg, with one tankful recording a best mpg of 43.0 and worst tankful at 28.7 mpg. The EPA rates the Jetta diesel at 34 mpg in combined driving, so Edmunds is doing a little better than the EPA predicted.

For USA nationally, diesel fuel is about 23 cents per gallon (8%) more expensive than regular gas. That difference drops to 15 cents in the Midwest, and only 7 cents more expensive than gas in many parts of the West.

Chip Haven

In February I first noticed a shift in relative fuel prices. Since 2004, diesel has been the highest priced fuel in CA. At times (2008) by a substantial amount. This came after decades where diesel was consistently less expensive than mid-grade gasoline.

In Feb I first noticed that diesel was well below premium grade and slightly below mid-grade gasoline.

No idea what has changed, but it sure is welcome.

 

[dzzz]

It's too bad VW has slipped in quality.

For trucks, I find CNG + diesel, and biodiesel, more interesting than gas/electric hybrid technology. CNG prices are very nice in the west.

 

[haven]

The recent decision by the EPA to classify CO2 emissions as a pollutant means the Congress will create legislation to contol it. (Absent congressional action, the EPA will create regulations of their own.)

Diesel could become an important part of the auto industry's response to legislation that requires reduced CO2 emissions from cars and trucks. Diesel engines emit 1/4 to 1/3 the amount of CO2 compared to gasoline engines of similar power, perhaps because the run at lower rpm to produce the power. (I'm guessing here -- does anyone know why diesel produces less CO2?).

Hybrid gas/electric vehicles would help auto makers meet new regulations for CO2 control, too, but they would need to reduce the use of the gasoline engine, which means a bigger battery on board. It seems to me that a diesel/electric hybrid could meet the new regs with a smaller (thus cheaper) battery.

Biodiesel could also get a boost from the EPA decision. Biodiesel produces somewhat less CO2 than dino-diesel does.

I expect it will take a couple of years for Congress to produce legislation, and its effective date will be several years farther down the road.

Chip Haven

 

[charlieaarons]

\. Diesel engines emit 1/4 to 1/3 the amount of CO2 compared to gasoline engines of similar power, perhaps because the run at lower rpm to produce the power. (I'm guessing here -- does anyone know why diesel produces less CO2?).

Hybrid gas/electric vehicles would help auto makers meet new regulations for CO2 control, too, but they would need to reduce the use of the gasoline engine, which means a bigger battery on board. It seems to me that a diesel/electric hybrid could meet the new regs with a smaller (thus cheaper) battery.

Biodiesel could also get a boost from the EPA decision. Biodiesel produces somewhat less CO2 than dino-diesel does.


Chip Haven

Diesels produce 1/4 to 1/3 less CO2 than petrol engines at the same power output; not 1/3 to 1/4 as much. Due to increased thermodynamic efficiency. Burning diesel fuel actually produces slightly more CO2 per pound burned than petrol. A typical diesel molecule is cetane, or hexadecane: C16H34, or 2.125 hydrogens per carbon. A typical petrol molecule is octane, C8H18, 2.25 H per C. Each has about (within 1%) the same energy per unit weight, so the carbon percentage of diesel is slightly higher than petrol. But that is very much overweighed by higher thermodynamic efficiency due to several factors: higher compression ratio, no throttling losses, sub stoichiometric combustion, improvements in area under curve in P-V diagram due to injection of fuel at TDC rather than earlier in compression cycle.
In the vast scheme of things, a 25 to 33% reduction of CO2 emissions with a proven, available power plant is a very good thing and a "no-brainer" in my book.
I don't think biodiesel is lower than petroleum diesel per unit energy; I'd like to see numbers.

Charlie

 

[R_Lefebvre]

To put it a little simpler, the Otto cycle (gasoline) is typically only about 25% efficient, while the Diesel cycle is typically 35-40% efficient. You can see this by the fact that diesel engines have trouble producing enough heat to warm a truck in the winter.

 

[dieselcruiserhead]

Thank you Charlie, that is about 100% correct.

The easy way to state is "carbon content" per unit and diesel does have more. Off the top of my head I believe carbon content per US gallon is gasoline in the low 70s, diesel in the low 80s, and biodiesel in somewhere in the high 70s. Carbon, in the case of all of these fuels, pretty much equals "power" and the difference is carbon content is the principle reason used to explain why biodiesel has an approximate 7% loss in power versus conventional diesel despite its higher cetane.

You will often hear "biodiesel emits less CO2" and this incorrect other than a slight technicality. The reduction of CO2 comes from lifecycle analysis. It is an easy mistake to make because biodiesel does make sweeping emissions reductions in nearly all categories primarily related to lack of pollutants in the fuel (that become airborne via the combustion process, sulfurs, etc.) The correct terminology is "biodiesel produces less greenhouse gas." This is in tune of about (a whopping) 80% reduction...

Because its core source is plant material it consumes significant amounts of CO2 to produce it, well over a 100% threshhold of CO2 produced via the emissions process. 16% of biodiesel (using an efficient process, it can be as is inefficient as 22%) is an alcohol which can be derived from agricultural or petroleum sources or even pig waste, so it varies considerably depending on source of the alcohol. The EPA has done a large sweeping study and the supposed reduction is "78%" on average, versus a conventional diesel, provided the land was agricultural land before it was used to grow biodiesel feedstock (which is the case most often in the US and Europe). In Europe they also use rapeseed varients (which are much more efficient that US soy) which is a non GMO version of Canola. And then finally they supposedly did a study on average CO2 production from manufacturing and shipping so the 78% includes that as well.

One of the large issues with biodiesel currently is its popularity in Brazil, where they are cutting down Amazon rainforest, the "lung of the earth" that supposedly consumes about 1/4 of CO2 itself.

Diesels produce 1/4 to 1/3 less CO2 than petrol engines at the same power output; not 1/3 to 1/4 as much. Due to increased thermodynamic efficiency. Burning diesel fuel actually produces slightly more CO2 per pound burned than petrol. A typical diesel molecule is cetane, or hexadecane: C16H34, or 2.125 hydrogens per carbon. A typical petrol molecule is octane, C8H18, 2.25 H per C. Each has about (within 1%) the same energy per unit weight, so the carbon percentage of diesel is slightly higher than petrol. But that is very much overweighed by higher thermodynamic efficiency due to several factors: higher compression ratio, no throttling losses, sub stoichiometric combustion, improvements in area under curve in P-V diagram due to injection of fuel at TDC rather than earlier in compression cycle.
In the vast scheme of things, a 25 to 33% reduction of CO2 emissions with a proven, available power plant is a very good thing and a "no-brainer" in my book.
I don't think biodiesel is lower than petroleum diesel per unit energy; I'd like to see numbers.

Charlie

 

[haven]

Thanks, Andre, Charlie and R_Lefebre, for the clarification.

I hope the mandate to reduce CO2 will help the auto industry
re-consider diesel for smaller vehicles in North America.

 

[charlieaarons]

A way to sequester atmospheric carbon:
Produce huge quantities of biodiesel, pump it into depleted petroleum reservoirs and salt caverns.
But wasteful of good concentrated chemical energy.

Charlie

 

[haven]

Attached below is a list of 14 of the small SUVs available in Germany. Overall, the average mpg of the 14 diesel-powered vehicles is 35.4 mpg.
I compared the mpg rating of the diesel SUVs with the smallest gasoline engine in a similar vehicle in USA. For the gasoline counterparts in USA, the average highway mpg is just 24.7, according to EPA ratings.

That's a 43.7% improvement in mpg when using the small diesels.


Suzuki Grand Vitara 1.9 DDiS 33.6 25 34.4%
KIA Sportage 2.0 CRDi LX 2WD 33.6 25 34.4%
Hyundai Santa Fe 2.2 CRDi GLS 2WD 33.6 24 40.0%
Hyundai Tucson 2.0 CRDi VGT GLS 2WD 33.6 25 34.4%
Mercedes GLK 220 CDI 34 21 61.9%
Mitsubishi Outlander 2.0 DI-D 35.1 25 40.4%
Land Rover Freelander Td4_e 35.1 22 59.5%
Audi Q5 2.0 TDI quattro 35.1 26 35.0%
Toyota RAV4 2.2 D-4D 4x4 35.6 27 31.9%
Jeep Compass 2.0 CRD 36.2 25 44.8%
Honda CR-V 2.2 i-CTDi 36.2 27 34.1%
BMW X3 xDrive20d DPF 36.2 24 50.8%
Subaru Forester 2.0D 37.3 26 43.5%
VW Tiguan 2.0 TDI 39.9 24 66.3%

source: http://www.autobloggreen.com/2009/0...esel-suv-cuv-crossovers-available-in-germany/

 

[haven]

Last week, for the first time in more than a year, the national average price per gallon for No. 2 diesel fuel is less expensive than regular gasoline.

Here are the stats from the US government agency that tracks fuel prices

Region..........Regular Gas....Diesel
U.S. -----------$2.24-------$2.216 per gallon

East Coast--------2.214------2.255
..New England----2.249------2.395
..Central Atlantic--2.238-----2.386
..Lower Atlantic---2.187-----2.186
Midwest-----------2.257------2.156
Gulf Coast---------2.134-----2.198
Rocky Mountain---2.181-----2.270
West Coast--------2.368-----2.329
..California--------2.424-----2.337

source: http://tonto.eia.doe.gov/oog/info/gdu/gasdiesel.asp

So some regions still pay more for diesel than gas, while others pay less.
In southern Nevada, the low price for gas this week is $2.15, while diesel costs $2.19.

 

[haven]

Ford's new "EcoBoost" turbocharged, direct injected gasoline engine is getting a lot of favorable press these days, and with good reason. The 3.5L V6 produces close to 350 ft-lbs of torque from 1500 to 5250 rpm. Combined with Ford's 6 speed automatic, the EcoBoost engine is expected to deliver 17 mpg city, 24 highway in full-size cars like the new Taurus, and mpg almost that high in Ford's large Edge crossover. Ford will develop a version of the engine for the F150 and Mustang, too.

Ford is planning to use the EcoBoost V6 in places where it might have used a 3.0L diesel. Reasons for choosing the gas engine over diesel include cheaper manufacturing, lighter weight engine, and a lower sales price compared to a comparable diesel engine. Ford also points to the public's familiarity with the responsiveness of a gasoline engine as a reason to choose gas over a diesel powerplant.

Those are valid points. I think the real reason is the wide fluctuation of diesel fuel prices last summer. Ford, and other USA manufacturers, are concerned that another rapid rise in diesel prices could kill sales of diesel-powered vehicles.

Mercedes and BMW show us what the diesel alternative is like. The Mercedes E 320 Bluetec full size sedan with 3.0L V6 diesel is EPA-rated for 32 mpg on the highway. That's 33% better than the EPA numbers for the EcoBoost. BMW 335d is a compact sedan with I6 turbo diesel and EPA rating of 35 mpg highway.

As used in the Audi Q7 SUV, the 3.0L V6 TDI offers 406 ft-lbs of torque from 1750 rpm. Driven through a 6 speed auto transmission, the Q7 is rated by the EPA to return 17 city and 25 mpg highway. Not bad for vehicle with a 5500 lb curb weight, 3 rows of seats, and all wheel drive. That's at least 10% better than the Ford Edge with EcoBoost V6, and the Edge lacks all wheel drive.

Ford is right about the extra cost to purchase the vehicle. The Audi Q7 TDI costs about $4000 more than a Q7 with V6 gas engine and similar equipment. The federal government helps with a $1100 rebate when purchasing the TDI, so the out-of-pocket difference is about $3000. That may not deter people shopping for a luxury SUV, but it certainly would make a difference for people looking for a family sedan like the Taurus.

Let's hope USA and Japanese auto manufacturers continue their research into diesel engines, even if they don't immediately plan to use diesel.

Chip Haven

 

[charlieaarons]

Once can say that the 3.0L X5 35d is $3500 more than the 3.0 petrol engine version, but it is $4000 cheaper than the 4.8L petrol V8, which as 50 ft-lb LESS torque and comparable 0-60 figures, though far worse economy (about 45% higher consumption). I know that if BMW sold its' next to top of the line 330d, it would be only ~$1000 more than the 330i, with considerably higher torque figures.
What is the comparison pricewise between the Q7 diesel and Q7 petrol V8? If it's anything like the BMW SUV, the diesel is way more powerful than the base petrol motor and really compares to the V8.
My wife is still averaging 21.0 mpg in the X5 35d, 100% city driving.

Charlie

 

[haven]

GM engineers have made some progress with HCCI, the gasoline engine that runs part of the time on spark ignition, and part of the time on compression ignition. The engine uses computer control to change valve timing. When cruising along, the engine runs on compression ignition. When more power is required, the engine switches to spark ignition.

GM says that HCCI engines can achieve about a 15% improvement in fuel efficiency compared to a similar spark ignition engine, which is maybe half the fuel efficiency gain you might expect from a diesel. HCCI can be manufactured at a much lower cost than a hybrid. They also cost less than conventional diesel engines, which must be more robust to deal with stress created when a diesel engine accelerates.

http://www.autoblog.com/2009/05/26/general-motors-hcci-engines-now-run-from-idle-up-to-60-mph/

HCCI stands for homogeneous charge compression ignition. The technology was promoted by Mercedes under the name "DiesOtto," since the engine has characteristics of both diesel and otto combustion cycles.

 

[dieselcruiserhead]

A way to sequester atmospheric carbon:
Produce huge quantities of biodiesel, pump it into depleted petroleum reservoirs and salt caverns.
But wasteful of good concentrated chemical energy.

Charlie

The only thing is biodiesel seems to only last about 6 months to a year on average. It would have to be reproduced back into biodiesel. It has all the carbon but I would say its a different sort of energy I suppose... It would work though, possibly NOT too energy inefficient due to... gravity

Check out this map, from this excellent report by a Utah professor about carbon sequestration and algae biofuel....
http://www.utah.gov/ustar/documents/63.pdf