Over time and miles, your car might start to slow down. It might not accelerate as quickly as it once did; the engine may not run as smoothly as you remember, or the fuel economy may dip—but ...

The first thing you should understand is that direct-port, constant-flow fuel-injection—Hilborns, En-derles, Crowers, whatever—were never designed, nor intended, to be run on the street. All of these ...

Carbon build-up reduces fuel economy by restricting airflow into the engine, disrupting the fuel spray pattern from injectors ...