Need more gas mileage?By Jeffrey Yago, P.E., CEM |
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| Issue #96 • November/December, 2005 |
The news is full of glowing stories about new hybrid cars getting over 60 miles-per-gallon, and you are wondering what to do with that old gas guzzler as gasoline heads past the $4.00 per gallon range in some states after the New Orleans and Gulf Coast hurricane devastation. Technically, a hybrid car is still a gasoline engine powered vehicle, but it also includes a small battery powered electric motor. The Toyota Prius has a dual-motor drive, operating on its battery-powered electric motor during stop and go city driving, then switching automatically to a conventional, but downsized, gasoline engine for highway driving.
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Some hybrids do not switch between the gasoline engine and electric motor, as these models have both operating as a single unit. For example, the Honda Insight and Honda Civic use a small gasoline engine coupled to the transmission with an electric motor. The electric motor assists the small gasoline engine when added acceleration or speed is needed, and recharges its small battery pack during braking and downhill coasting. You also need to think about passenger room when considering a hybrid, as they are not all the same. The Honda Insight, for example, is basically a two-seat vehicle, while the Toyota Prius can seat up to five passengers.
Automakers sold over 55,000 hybrid vehicles in the United States leading up to 2005, but Toyota alone plans to sell over 100,000 hybrids this year. Hybrids cost about 20 percent more than a similar sized conventional gasoline engine vehicle, but can recover their higher initial cost in fuel savings. However, before you mortgage the farm and head for the dealership, you may want to consider several less expensive alternatives for higher fuel mileage.
In 1975, the United States Congress and President Ford passed a law that mandated raising the fuel mileage of all vehicles sold in the United States. The law was called CAFE (Corporate Average Fuel Economy) standards. This law required raising the average mileage of all cars a given manufacturer made (trucks and SUVs were exempt) from the then current average of 17.8 to 27.5 miles-per-gallon. Later, Congress added trucks to the list, but their mileage goal was a lower average of 20.7 miles-per-gallon. It is now over 30 years later, yet these minimum standards have not changed. Although many politicians wanted to include raising these CAFE standards as part of the recently passed Energy bill, it never made it.
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Most hybrids achieve their high mileage advantage during city stop and go driving, when an idling larger conventional engine is the least efficient. During higher speed interstate driving, the fuel economy of many hybrids will drop significantly, especially if the route is over mountainous roads. Many new hybrid vehicle owners are complaining that they are getting much lower gas mileage than advertised. Part of this discrepancy is due to the way the government mileage tests are conducted. The EPA guidelines were developed over 19 years ago, and specify that the published sticker gas mileage will be determined using a stationary car on a dynamometer test stand, while “simulating” different driving conditions. This simulation includes a top speed of 60 miles-per-hour, yet many of us drive 65 to 70 miles-per-hour commuting the interstate each day. Keep in mind that above 55 miles-per-hour, wind resistance increases dramatically, which lowers average mileage figures even more. Consumer Reports stated that independent testing of hybrid vehicles using real world driving conditions found mileage figures that averaged up to 40 percent below the EPA posted mileage figures.
The mileage chart on page 22 shows the most fuel efficient cars and trucks available in the United States. As you can see, many of these vehicle models have been available for years and would be excellent choices whether you are looking for a new or used vehicle.
Yes, you will achieve higher mileage figures with a hybrid vehicle than with a similar sized conventional vehicle, but the mileage chart shows there are still some excellent new and used non-hybrid vehicles that will double the mileage you are probably getting right now with your SUV or truck.
Many households are going to reconsider their mix of vehicles and how they are used now that high gas prices and long gas lines are back. Instead of two or three large SUVs in the driveway, I think many homeowners will utilize their newest SUV to combine multiple short trips and errands each day into a single multi-functional trip each week. If it’s not plowing through the snow, hauling something, or carrying three or more passengers, it will probably be parked. I think most households will be trading in at least one of their cars in the next year for a downsized and very fuel efficient vehicle for short errands and daily commute, which may also include ride sharing for the first time.
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If you really need a vehicle that gets great gas mileage for a very long daily commute, there are still some excellent buys without going the hybrid route. For example, the Toyota Corolla, Honda Civic, and GEO Prizm have been quietly providing 30 to 40 miles-per gallon for their owners for years.
If you really want fuel economy, more than half of all new cars sold in Europe, where gasoline prices are even higher, have diesel engines. A diesel engine is heavier and more expensive than a conventional gasoline engine. Diesel engines operate at a lower RPM, yet still exceed the torque of a gasoline engine. Lower operating RPM means much longer engine life and much higher combustion efficiency. Many large diesel truck owners easily achieve more than 300,000 miles before major engine repairs are required, and many luxury European diesel cars provide this same reliability. Vehicles with a diesel engine option are returning to the American shores, with the introduction of the diesel-powered Jeep Liberty in 2005.
Although Jeep has been offering this diesel option for years in Europe, this is the first time it has been available in the United States. Volkswagen has offered a diesel option for their popular Jetta for several years now, and other car manufacturers will be getting on the bandwagon since new diesel engine technology has significantly reduced engine noise, and greatly improved acceleration and cold starting performance.
Part of the improved mileage being achieved by hybrid vehicles is due to their lower weights and much more efficient transmissions and drives. These performance improvements are also starting to find their way into conventional vehicle designs to increase their fuel mileage. It is clear that we are finally starting to take energy and fuel efficiency more seriously. However, it’s unfortunate that it took a national catastrophe on top of already developing shortages in the world oil markets to move us in that direction.