For a gas engine, 14.7:1 is the mixture of air to fuel that we always strive for. The O2 gauges use O2 sensors that were originally manufactured to make your fuel injection system work. The non-wideband gauges are based on some of the earliest O2 sensors available. The early O2 sensors came from early fuel-injected cars and basically told the computer if it was running rich or lean, and the computer adjusted the other way to compensate. As fuel injection systems became more complicated and the computers faster and more powerful, engineers were able to come up with a more sensitive sensor that actually fed more than just “lean” or “rich” back to the computer for much finer control of the air/fuel ratio. In gauge-speak, the later O2 sensors and gauges such as this Auto Meter 6178 are considered wideband units and are much more reliable for tracking how an engine is running than the non-wideband gauges.