Some things look great on paper but, despite the overwhelming logic of arguments in their favor, never seem to become mainstream.

Consider Esperanto - the 'universal language,' developed in 1887 to "foster peace and international understanding".

Like diesel fuel, Esperanto has its enthusiasts - it is relatively easy to master and has enjoyed continuous usage by a community estimated at between 100,000 and 2 million speakers. Esperanto is employed in world travel, correspondence, cultural exchange, conventions, literature, language instruction, television and radio broadcasting.

But, we're still waitiing for that 'peace & understanding' thing. And, see how far you get if you burst into Esperanto at the TSA security checkpoint at the airport. Peace & understanding, my ass.

In the days of videotape, Beta was a technically superior format than VHS. But, people wanted long recording times and were too lazy to swap out tapes. The mob had spoken: VHS prevailed; Beta died as a consumer recording format. (I still chuckle when I see that old Simpsons episode where Homer patronizes VHS Village with the small type on its sign: "formerly The Beta Barn.")

There are the positive facts about diesel:

1. It has approximately 18% more energy per unit of volume than gasoline. 2. It also takes less refining to make diesel fuel. 3. Properly designed diesel engines are actually more efficient than gasoline engines. As a result, people with diesel engines enjoy better gas mileage.

Here's the negative side of things:

1. Diesel fuel stinks and it will get your hands crummy if you don't wear gloves. Not good if you're on your way to an important sales call. Or a hot date. 2. In America, diesel engines have a bad rep from failed '80s cars. (Thank you, General Motors.) 3. Diesel pumps are harder to find than gasoline. 4. In many areas of the U.S., diesel costs much more than Regular gas. (In these parts, it costs more than Premium.) 5. Diesel engines are noisy. Not as much as they used to be ... but who wants to spend big bucks buying a brand-spankin' new car that sounds like an ancient air-cooled VW with bad valve clatter? 6. Diesel exhaust is dirty and smelly. Diesel buffs claim this is no longer be accurate ... but, hey, have you ever been stuck behind a belching yellow school bus? 7. Diesels cost more - $1,000-5,000 depending to the model chosen. Prospective buyers shrug and quip, "Hell, for that kind of extra money, I could buy a hybrid."

In countries where fuel is much more expensive than it is in the U.S., diesel is making inroads. Austria and France already have diesel penetration rates of around 50%. Diesel pump prices in Europe are - on average - 16% cheaper than gasoline. And did you ever ... ummm ... smell Europe? The B.O. masks that diesel aroma pretty well.

U.S. consumers may be interested in diesel vehicles when fuel prices hit the $7-8 per gallon range. Until then, diesel-powered passenger vehicles will probably be niche players in the U.S.

I don't know how to say 'niche player' in Esperanto. (posted 3/8/08)

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Update (5/20/08): Paul Niedermeyer of TTAC notes that "expectations for VW's 2009 "60 mpg" TDI Jetta "Prius killer" ran high. And VW threw plenty of (diesel) fuel on the heated passions of oil burner fans.

Press materials just a few weeks ago predicted EPA city mileage numbers "in the 40s" and highway mileage "as high as 60 mpg." The EPA has released the numbers and they … suck. We're talking 29/40 for the DSG version; 30/40 for the stick. Combined mileage: 34 mpg. The Prius' 46 mpg combined mileage is a whopping 35 percent higher.

Diesel fuel is running 20% higher than unleaded. Annual fuel costs for the two (15k miles): Jetta TDI: $2010; Prius: $1,240." Ooops.