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Diesel fuel: Strengths and Weaknesses

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Details on biodiesel fuel.

Damien Civiello

Consider this:

1) A gasoline engine (or spark-ignition if you want to get technical) is at BEST, 20% thermally efficient, and most of these are these small new 4-cylinder vehicles. On the other hand a diesel is close to 40% thermally efficient. In many cases, such as the new Mercedes Diesel, they have to actually add a heater, two in reality, one electric for immediate heat and the other a diesel burner just to provide cabin heat.

2) In a recent issue of the SAE (society of automotive engineers) magazine they did an article on both Cummins and Detroit Diesel (which is owned by DCX) developing a smaller displacement diesel (or compression-ignition engine) of about 4 liters for use in sport utility vehicles. Their test bed was a Dodge Durango with a 5-speed and a 5.9L V8.

The Cummins unit was a modified version of one of their industrial engines which did well but was not as powerful. The Detroit Diesel motor was a brand new design specifically for this market. Both were turbocharged and mated through the same 5-speed.

The results with the new Detroit Diesel motor was impressive. Gas mileage improved to about 22 city and close to 30 highway (almost the same as my Shadow), towing and hauling capacity were increased, and 0-60 times were almost identical (off by about 0.1 sec in favor of the 360 [gasoline V-8]). The diesel was no louder than the gas engine and was designed with a minimum life of 100,000 miles of operation, and this was just the first generation prototype without all the bugs worked out. The good part is that since DCX owns Detroit Diesel this motor has a good chance of making it.

I've got lots more info but since most of you have probably deleted this by now I'll just say that one reason I love the 3.0 is that I have gone up some pretty steep hills here in central PA and watched in amazement as the car downshifts while climbing the hill to get closer to the 2K RPM sweet spot! Hell, my truck fights the whole way up this same hill because of the low gearing, the Shadow loves it.

One last thing, the 413 is approx. 6.7 liters, I was curious since I have one, it's one impressive motor. I have enough power to twist the back end around from a standstill yet if I stay out of the 4 barrels I got almost 17 MPG from my hometown to Carlisle PA (about a 2 hour drive south of me) and back, including the time I spent running around town.

Bob Sheaves wrote:

[In response to comments about diesels smoking]

My 92 VW diesel is due for its first inspection next month. After some digging, I've found out that unlike the computerized exhaust analisis for gasoline engines, I only have to pass a visual inspection [Canadian provincial law]. No leaks, no heavy black smoke equals a pass! I don't know if this is because the smaller number of diesels doesn't justify the cost of the equipment or because the fumes aren't considered toxic enough. I'm guessing it's a combination of low toxicity and lower vehicle numbers have less overall impact on the enviroment. I have no solid facts, but I have heard that diesel fumes, although ugly black, and smelly, are actually less damaging to the enviroment than "invisable" gasoline exhaust fumes. I'd be very interested in hearing other opinions on that, it's not my field of expertise, just an interest.


One thing I would like to make clear...if a diesel is "smoking" under any other conditions than full throttle and high load, there is something wrong with it, generally too much fuel is being injected. Under idle, or normal operating conditions found in the midwest of the US and Canada, there should be NO smoke coming from the tailpipe.

That being said, [if yours smokes], one thing you might look into is a commercial "additive" to diesel fuel that is available at most large truck stops-this is (without naming brand names) pure biodiesel intended to be mixed in the tank at a B20 or less rate. Look for the words "naturally produced oil" or "biodiesel" on the side of the can under ingredients. This product will (in proper mixture levels) reduce the amount of smoke an older, worn engine will put out...AND give you that nice McDonalds smell...LOL!!!


The US government taxes diesel and gasoline differently, but the net result is that diesel is less expensive from the refiner. The big difference is in the way the STATES tax diesel. This is why the price of diesel varies far more than gasoline as you travel state to state.

Additionally, because of all the other uses for diesel, seasonal demand comes into play far moreso than in gasoline. In most other countries, the "federal" taxes are far less on diesel. Here in Japan, a liter of gasoline is currently around 112 yen. One liter of diesel is running 78 yen to 98 yen, depending on the engine displacement of the vehicle it is going in. Diesel fuel went down today (Wed., 2 May 2001) by about 3 yen at the station I generally fill up at.

In Germany and Czechoslovakia, the tax structure is set such that biodiesel taxation is less than 1/2 that of petroleum diesel, to encourage use of a renewable fuel. This means that gasoline is around $3.18, diesel #2 is about $2.96, and biodiesel (B100) is about $1.91, all per US gallon.

Central Editorials Page | Details on biodiesel fuel, click here.

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