Wednesday, February 20, 2008

Diesels vs. Hybrids

The original Toyota Prius came on sale in 2000, when the Ford Explorer was the bestselling vehicle in the US and sales were at their peak. Last year, Prius sales soared nearly 70% to outsell Explorer. This says something about changing attitudes, but are hybrids all they are cracked up to be? Enthusiasm for hybrids seems overblown to me. After all, the energy still comes from gasoline, so the only saving is due to regenerative braking and switching off instead of idling.

Consequently, highway mileage tends to be lower than city mileage, so the benefit you get from a hybrid will depend a lot on your driving mix. Last year, the 2007 Prius topped the EPA’s old fuel efficiency ranking with 60 mpg in the city and 51 mpg on the highway. This year, the EPA has changed the test cycles, so that for most cars both mileage estimates go down 2 or 3 mpg. The change is more detrimental to hybrids, however, and the Prius is now rated at only 48 mpg city, 45 mpg highway.

According to ConsumerAffairs.Com, many Prius owners disputed the 2007 mileage numbers, reporting average fuel economy of 43 mpg. (See If you own a hybrid, I would like to hear comments about how well they perform in real life, as opposed to the EPA test cycle.

I expect to see growing interest in diesels as a more practical and reliable alternative to hybrids, typically giving about 30% better mileage than equivalent gasoline engines. Also, the engines tend to last longer.

A few manufacturers have introduced diesels recently in the US, notably Mercedes with the E-class Bluetec. Rated at 23 mpg city 33 mpg highway (using the new test), it is very economical for a mid-size luxury car. The Jeep Liberty is also available as a diesel, as are three Volkswagen models. BMW and Audi will follow, as will Honda (including its Acura brand). Subaru has a new diesel version of the Legacy in Europe and that might get to the US next year. Audi might even let us have their 80 mpg A2 TDI, also available in Europe.

The 2008 Volkswagen Jetta TDI is currently probably the nearest US-available diesel to compare with the Prius. It does cost a bit more (it lists at about $25,000 against $22,000) but you are probably more likely to get a deal. EPA numbers are 36 mpg city, 41 mpg highway on the new test. And by all accounts you will have a lot more fun.

But Americans do not seem to like diesels. A recent Kelley Blue Book Marketing Research study found that only six percent of shoppers think diesel is most likely to succeed in becoming a mainstream vehicle power-train type, compared with 40 percent for hybrids, 20 percent for hydrogen fuel cell and 17 percent citing flexible-fuel systems. (Flex fuel vehicles offer the dubious advantage of allowing one to switch to subsidized corn-derived ethanol, which we now know results in more emissions than gasoline as well as enriching corporate farmers and taking corn out of the mouths of poor Mexicans.)

Apparently the main reason for the dislike is that diesels are perceived as noisy and smelly, but this is way out of date. In Europe, diesel already is a “mainstream power-train type”, outselling gasoline powered cars in most markets. If you rent a car in Europe you are likely to get a diesel and you probably won’t even notice the difference. The main difference – apart from filling up from the right pump – is prodigious low-end torque and a corresponding lack of any need or ability to use high rpm. (Enthusiasts may miss this, but most Americans choose an automatic anyway; these drivers are unlikely to care.) Pre-heating when necessary is automatic and quick.

I think the Kelley Book survey is correct in that diesel is not the final answer, but then neither in my opinion is hybrid. I think the future will be either pure electric or hydrogen. The latter may be powered by fuel cell or internal combustion engine as BMW are experimenting with. And of course the electricity or hydrogen has to be produced from a clean source. (Kelly did not even ask about pure electrics, by the way.)

In the shorter term, because of the lack of infrastructure for hydrogen or pure electric, look to diesel and plug-in hybrids.

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