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Choosing the Right Engine Size
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Deciding which new vehicle to purchase is made more difficult by the wide array of engines available for each model. A buyer might think that small engines offer better fuel economy and larger engines will deliver performance. In truth, tiny engines don't always yield the highest fuel economy, and big engines don't always provide the best performance.
To better understand which engine is best for your needs, it is beneficial to spend some time understanding the relationship between engine size, horsepower, and torque. It is also helpful to understand government fuel economy guidelines.
Horsepower, torque, and engine size
The sudden rush of power felt when stepping on a vehicle's gas pedal is measured as horsepower and torque. Horsepower is the amount of force an engine can produce. Torque is how that force is applied to turn the wheels. In almost all cases, increases in horsepower and torque come at the expense of fuel economy.
Small engines, with fewer cylinders, traditionally have less horsepower and torque; as a result, they burn less fuel. Because they are smaller and more fuel efficient compared to their large-displacement counterparts, these engines often weigh less. This allows the vehicle to handle better. Smaller engines will have fewer parts to service and be less expensive to maintain during the life of the vehicle. Small engines should not necessarily be considered as underpowered. Turbochargers or superchargers can make smaller engines very powerful, while consuming less fuel than larger engines.
Engines with six or more cylinders are generally more powerful than smaller engines. With larger cylinders and increased complexity, this type of engine burns more fuel to generate the horsepower and torque needed to move heavy loads or pull a trailer. For towing or carrying large loads, consider an optional diesel engine. Today's diesel engines are quiet and cleaner-burning than those offered in the past, and generate plenty of power with reasonable fuel economy.
Understanding CAFE guidelines
Fuel economy information is listed on the window sticker of every new vehicle sold in the United States, as required by the federal government. The guidelines, known as Corporate Average Fuel Economy (CAFE), were introduced following a Congressional act in 1975. CAFE was designed to reduce energy consumption by requiring manufacturers to increase the fuel economy of their cars and light trucks. Under the CAFE program, a test cycle is used to estimate city and highway fuel consumption in miles per gallon (mpg), and the test results are listed on the vehicle's window sticker.
CAFE ratings should be used only as a guide to fuel economy. They are based on a now-obsolete series of tests, and most consumers will find their actual mileage to be lower than what is listed on the window sticker. More than three decades after enactment, CAFE testing will be updated to better reflect real-world driving conditions for model-year 2008 vehicles. Consumers will see revised CAFE numbers for 2008 model-year vehicles as they are introduced for sale throughout 2007.
Making the decision
When choosing your next engine, take a close look at the CAFE ratings on the window sticker and the engine specifications in the brochure. Often times, the horsepower and torque differences between engine sizes may be insignificant enough to justify a price premium, and you may want to choose a less expensive engine option for your needs. While each type of engine operates differently, their fuel economy, horsepower, and torque ratings often reveal much about how they will perform.
Want to learn more about fuel economy? For more information about CAFE standards and fuel efficiency, visit the Environmental Protection Agency's Web site www.fueleconomy.gov. Mike Harley
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