Hybrids and Diesels Face Off for Fuel-Efficient Choices

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Inside this Article

Hybrid Honda Accord
Hybrid Honda Accord
Diesel Volkswagen Jetta
Diesel Volkswagen Jetta
Diesel Volkswagen Beetle
Diesel Volkswagen Beetle
Hybrid Toyota Highlander
Hybrid Toyota Highlander
Diesel Jeep Liberty
Diesel Jeep Liberty
Hybrid Honda Accord
Diesel Volkswagen Jetta
Diesel Volkswagen Beetle
Hybrid Toyota Highlander
Diesel Jeep Liberty

If you are in the market for a more fuel-efficient car, but find yourself spinning your wheels over figuring out the best choice, here’s a closer look at the two major options available—gasoline-electric (hybrid) autos and diesel-engine vehicles.

Hybrids have been touted as the champs for lower fuel costs and fewer environmental impacts. But the higher prices of hybrids can be a deal-breaker for those in the market for more fuel-efficient wheels. Are diesel engine vehicles a viable alternative? Here’s Aesop’s fable of the tortoise and the hare—twenty-first-century style.

Purchase Price & Payback Time

Whether you buy a hybrid or a diesel, you’ll pay a premium over a gasoline-engine vehicle, which you expect to recoup in the form of fuel savings. Compared to their nonhybrid counterparts, hybrids generally have an even greater difference in their purchase prices than diesels. Why? Hybrids have two power plants: one gasoline and one electric. You can’t get two power plants for the price of one, and the hybrid’s sophisticated storage battery and electronic controls come at a price.

But with federal tax credits (from $600 to more than $3,000), hybrids could kick into overdrive to sprint ahead of the diesel in this event. So hybrids win, right? Not according to the photo finish. First, tax credits vary considerably from model to model and are slated to be reduced as hybrid sales figures hit predetermined levels. The Purchase Price & Payback table below shows how long you’ll wait for your reward for certain models based on November 2006 fuel prices. The purchase premium is the difference between the hybrid or diesel’s price and the price of a stock gasoline version of the same model. Of course, this difference (and the payback time) depends on how many miles per year are driven, and the price of gasoline and diesel fuel. But in most cases, for faster payback, the advantage goes to diesels.

Fuel Economy

Both diesels and hybrids outperform their gas-engine counterparts, although real-world hybrid fuel mileage reported by individual drivers is often lower than the U.S. Environmental Protection Agency’s (EPA) estimates. (In the cases of driver-reported fuel economies of Mercedes E320 Cdi and Volkwagen Jetta TDI models, diesels tend to outperform their EPA ratings.)

Case in point: The Honda 2005 Civic Hybrid’s EPA rating is 48 miles per gallon, but when Consumer Reports tested it in real-world driving conditions, it got 36 mpg. And Autoweek reported in its November 2005 issue that their long-term testing of the 2005 Prius realized 41.2 mpg over a 16,000-mile span of mostly highway driving—far below the EPA’s combined (city/highway) estimate of 55 mpg, and well below its highway rating of 51 mpg. The EPA is changing their test protocol for 2007, and new ratings are expected to better reflect real-world mileage for future models. (You can find driver-reported fuel economy at www.fueleconomy.gov/feg/findacar.htm.)

Another quirk of hybrid fuel economy is that their city mileage frequently surpasses their highway mileage. For example, a 2006 Toyota Highlander SUV hybrid is EPA-rated at 33 mpg in the city and only 28 mpg on the highway. Why? A full hybrid uses its electric motor more often in stop-and-go city driving, with the gasoline engine off completely (or only lightly loaded), especially at or below 25 mph. Conversely, at highway speeds, the electric motor and its batteries are idle, and their extra weight can actually penalize fuel mileage. If you’re a prospective hybrid buyer and you don’t do much stop-and-go city driving, your return probably won’t be as good as another hybrid driver who travels more stop-and-go urban miles. On the other hand, if you drive exclusively in the city, it may be difficult to rack up enough miles required to recuperate the premium you paid for the hybrid.

Even with the hybrids’ lower-than-reported fuel economy, generally, they are still competitive compared to similarly sized diesel vehicles. Take the 2006 Toyota Prius, for example, which has a driver-reported combined fuel economy average of 47.2 mpg, and the 2006 VW Jetta TDI, which has an average reported combined mpg of 41.9.

Fuel Costs

Diesel used to be cheaper than gasoline. But these days, in most areas of the country, it costs even more than premium gasoline. And biodiesel is even pricier. So the gasoline-electric hybrid wins the fuel-cost event hands down, right?

Not so fast: Using straight or waste vegetable oil (SVO or WVO), which can often be obtained at no cost from restaurants, can blow the doors off any hybrid when the mpg ratings of the vehicles are similar. Of course, while the fuel can be sourced at no charge, you’ll pay another price if you don’t like getting dirty—grease-gathering can be messy, and you’ll need a place to store and filter the veggie oil. You’ll also need to pony up some greenbacks to install a vegetable-oil conversion kit, which typically includes an auxiliary fuel tank, additional hoses, fuel-heating apparatus, and an under-the-hood veggie-oil fuel filter. Kit prices usually start at about $800 (uninstalled).

The amount you’ll shell out for fuel each year depends on how much driving you’ll do—and where (in the city or on the highways). We’ll call this event a draw.

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