The Best Specs & Fuel Mileage for Class 8 Trucks

by Kristin Jennifer
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dump truck image by Leticia Wilson from

Class 8 trucks are those trucks that weigh 33,000 pounds or more. Examples of class 8 trucks include dump trucks, cement mixers and tractor trailers. Typically, class 8 trucks average 5 to 8 miles per gallon. Fuel mileage improves by increasing fuel economy. Increasing fuel economy comes down to choosing the right specifications, or "spec'ing," that will be built into the truck at the time of purchase.

How You Move

Fuel is used to move the truck through the air and over the land. The more resistance a tractor trailer encounters due to low aerodynamic design, the more fuel it will need to traverse the highways. Aerodynamic spec'ing improves fuel economy by a 2 to 1 ratio. For every 2 percent increase in aerodynamics, truck owners can expect a 1 percent increase in fuel economy. Aerodynamic spec'ing includes choosing a body design that increases airflow across the cab and over the trailer.

Underneath It All

Tractor trailers gain in fuel economy by adding single wide tires or oil bath seal wheels on non-drive axles. Hybrid engines reduce reliance on fuel for takeoffs, which can gorge fuel. Automatic transmissions control fuel economy by controlling shift logic by computer program. To reduce fuel consumption, engines also must be adequately powered to handle the load and route that the truck travels. Dump trucks and cement truck spec'ing must stay away from an emphasis on horsepower. Since most dump trucks spend most of their time at speeds of 10 to 20 mph, spec'ing should focus on purchasing advanced technologies that improve the efficiency of the engine.

Driver Behavior

Fuel economy can be improved by giving truck drivers tools to better control speed. Adding cruise control helps drivers maintain speeds of 50 or 60 mph, which offers the best fuel economy. Fuel economy displays also aid drivers in monitoring fuel usage during shifting into first and second gears. Heavy- footed drivers tend to spend more fuel during starts from stops than at any other time.

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