Many drivers choose to make performance modifications to customize the way their vehicle performs. Commonly, drivers assume that since the adjustments give their car the ability to make more horsepower and go faster, these changes will have a negative effect on their gas mileage. Although conventional wisdom lends some credence to such sentiment, it’s actually somewhat misinterpreted. The truth is that there are a variety of common performance add-ons that actually increase a vehicle’s gas mileage with normal driving conditions.
Performance modifications can mean many things, though most performance modifications are engine-centric. They consist of either engine modifications, increasing the displacement, improving the compression ratio, the air/fuel mixture ratio or suspension modifications.
It’s necessary to understand how performance modifications work. Ultimately, their end goal is the same—they generate more power. There are two main ways to give the motor more air and fuel—modifications that increase capacity and those that increase efficiency.
These are the “big boy” power adders that include turbo and superchargers as well as nitrous oxide. This category also includes anything that increases the displacement of a car’s engine (such as overboring or “stroking” an engine). These modifications function by increasing the internal capacity of the motor to take in the air/fuel mixture. Turbo and superchargers do this by pressurizing the air so that it contains more oxygen and can burn more fuel. Boring or stroking increases the displacement of the cylinders, and nitrous oxide actually chemically adds oxygen that can be combined with extra fuel. All of these modifications will reduce a vehicle’s fuel mileage, sometimes drastically, but there is an exception for some applications where turbocharging can have a positive impact on fuel consumption to a point.
Modifications that increase efficiency have a positive effect on gas mileage. They work by removing restrictions that reduce the flow of air into and out of the motor. They increase the motor’s ability to take in and burn air and fuel but not forcibly so like capacity based modifications. Efficiency-based modifications that allow the engine to take in more air and fuel include high-flow filters and intake kits, restriction and backpressure reducing exhaust systems and mufflers, increased capacity manifolds and port/polish work.
Other Efficiency modifications include high-performance spark plugs and wires, performance ignition systems and modifications that increase engine compression (high compression pistons, or block “slabbing”). A motor with these types of modifications have increased efficiency and thus the ability to take in more air and fuel for more power. They also allow the engine to do more with less and thus reduce overall fuel consumption.