The Hemi engine gets its name from its shape--the cylinders and valves are arranged in a semi-circle, or hemispherical shape. This gives better horsepower and torque. Hemi engines are large--eight cylinders, usually--and thus tend to use a lot of gas. Some of them use the MDS, or multiple displacement system, which allows them to run on just four cylinders, greatly increasing their fuel efficiency when the power of a V8 is not needed. When more power is necessary, the MDS automatically engages the other cylinders. Even if your Hemi doesn't have the MDS, following some simple fuel-saving tips will still increase your fuel economy.
Keep your cruise speeds to 65 miles per hour or lower. This helps ensure that your Hemi engine will run on four cylinders, and thus, save gas.
Accelerate gradually. This helps ensure that the Hemi stays in four cylinder mode and uses less fuel. If you stomp down on the gas pedal, it'll use more cylinders and guzzle gas.
Maintain steady speed whenever possible. If you have cruise control, use it. This also helps to ensure that the Hemi engine continues running on four cylinders.
Install a high-performance air filter, like the FRAM Air Hog or K & N filters. Many car enthusiasts agree that these increase gas mileage.
Follow standard fuel-economy tips, including making sure your oil is changed regularly, keeping all tires equally inflated and planning your trips out in advance so that you make the most efficient use of each outing.
Consider installing a new, high-flow air intake and a wider diameter exhaust system. Many car nuts liken a narrow intake and exhaust to trying to breathe in and out through a narrow straw. Supplying a wider straw--the high-flow intake and wider diameter exhaust--places less strain on the engine, offering better gas mileage.
