Different Engines, Higher Mileage: Gas-Electric Hybrids and Diesel Engines Go the Distance

Since the earliest Model T Ford, engines using gasoline have turned the wheels of America's cars. But now there are alternatives. Movie star environmentalists Susan Sarandon and Tim Robbins drove their gas-electric hybrid car to the Academy Award ceremony as a political statement. And mechanically minded gearheads love their diesel cars for the engines' efficiency and durability.

But the best reason for you to consider either a hybrid or a diesel vehicle are those numbers on the fuel pump at the filling station. Both can boost your mileage by 30% or more over comparable gas-only vehicles--with some models hitting 50 miles per gallon (mpg).

The combination of high gas prices and environmental concerns has led to better-than-expected popularity for both hybrids and diesels. Toyota sold 20,000 of its hybrid Prius sedan last year--a tiny fraction of the total auto market but enough to establish that it is a profitable niche, the company says. The Volkswagen Beetles and Jettas that now come with diesel options are about to get company. Jeep's small Liberty SUV will come in a diesel version next year, and Mercedes will offer a diesel option in its E-class sedan for 2004. Surprisingly, 27% of respondents in a J.D. Power and Associates survey said they would choose a diesel if it matched gasoline engine emissions and performance.

To be sure, both diesels and gas-electric hybrids have some drawbacks you should consider before making any decision to buy one. Hybrids cost more than their gas-only equivalents (for example, about $2,500 more for a $21,010 Honda Civic Hybrid than for a comparably-equipped regular Civic EX). This is partly offset by the $2,000 tax deduction you can take when you buy any of the hybrid cars. And it remains to be seen if postwarranty maintenance costs for the hybrid systems could be higher than for regular cars.

Some diesels, on the other hand, cost less than their gas counterparts--about $1,250 less for the diesel New Beetle. The disadvantage is in finding fuel; it isn't available at every filling station. You always can find diesel fuel at truck stops where the 18-wheelers fill up, but that may mean some extra effort.

How they work

Hybrid cars get more than 50 mpg by using both a gasoline engine and an electric motor powered by batteries. The gas engine recharges the batteries as well as powering the car. Unlike previous cars with electric engines, you never have to plug them in. In the Toyota Prius--the best-selling hybrid so far--the electric engine takes over entirely at low speeds. As a result, the Prius has a higher EPA (Environmental Protection Agency) mileage rating for city driving--52 mpg compared with 45 mpg on the highway; that's the reverse of conventional cars. Toyota plans a redesigned 2004 Prius for sale in fall 2003, which the company says will be larger inside and will get about 15% better mileage than the original Prius.

The competing Honda Civic Hybrid works a little differently: The electric engine kicks in for more power on hills or when you put the pedal down for sharp acceleration. The Honda is rated at 46 mpg for city driving, 51 mpg on the highway. Honda's two-seater hybrid Insight, both lighter and less practical than the Civic and Prius, gets the highest mileage ratings--61 mpg in the city, 68 mpg on the highway. In all these cars, both gas and electric engines shut off at stoplights or other full stops. Once you get used to that total mechanical silence during red lights, driving a hybrid is much like any other car.

Diesel engines get as much as 40% better mileage because they compress air and fuel in the cylinder under high pressure, ignite without a spark, and get more energy from the fuel. Diesel engines were invented more than 100 years ago and are well-proven as power plants for large trucks and buses. More than one-third of new cars sold in Europe are diesels; with gasoline far more costly there, mileage matters. Modern diesel engines--often equipped with power-boosting turbochargers--are nothing like the noisy, smoky versions many remember from the 1970s and 1980s. The top-mileage U.S. diesel, the Volkswagen New Beetle, is rated by the EPA for 42 mpg in city driving, 49 mpg on the highway.

Should you switch?

To see whether a gas-electric hybrid or a diesel vehicle might work better for you, ask yourself:

How much space do you need? Right now, hybrid power plants come only in small cars, the Toyota Prius (same size as a Corolla) and the Honda Civic Hybrid and the two-seater Honda Insight. However, the redesigned 2004 Toyota Prius will be larger inside and rated as a midsize car. For more space, Ford's small SUV Escape will offer a hybrid version next year. Diesels also are mostly in small cars now. But the Jeep Liberty SUV and the Mercedes E-class sedan next year will provide bigger diesel options.

Diesel fuel isn't available at every filling station.

How much do you care about acceleration? The hybrid Honda Civic and the Toyota Prius move out on the highway as well as their gas-only counterparts. But if you want a little more kick with your high mileage, the turbocharged diesels from Volkswagen will deliver.

How much do you care about environmental issues? Hybrid cars cut down sharply on the emission of smog-forming air pollutants. With diesels, you're helping to lower greenhouse gases implicated in global warming just by burning less fuel. But environmentalists caution that diesel emissions of soot are too high without improved low-sulfur fuel, not yet available here.

How much do you like the latest high-tech gadgets? Hybrids are fun to drive, but in a different way. Readouts on the dash show mpg at any given moment plus your average mileage for a trip. It feels like a video game for adults, and it's pretty exhilarating to see a temporary readout of more than 70 mpg. In diesels, the instrument panel looks the same as in an ordinary car.

Scientists believe the car of the future will be powered by hydrogen fuel cells--a program the Bush administration is backing with research funds. But such cars--where hydrogen is converted to electric current stored in batteries that then run an electric engine--are at least 10 years away from widespread use. For now, hybrids and diesels are the best alternatives.

Jerry Edgerton is an automotive writer whose work has appeared in Money and other national magazines. He also is the author of the book "Car Shopping Made Easy."

Published July 7, 2003