Most drivers know the advertised miles per gallon (mpg) fuel economy ratings of their vehicles. (If you don't, visit Fueleconomy.gov.) But in many cases, you'll rarely realize those published numbers during everyday driving, regardless of how accurately you calculate your actual mpg each time you fill up the fuel tank.
Diverse driving conditions, dirty air filters, low tire pressure and mechanical issues can all contribute to lowering your overall fuel economy. But one of the most overlooked factors is the one behind the wheel: the driver.
The U.S. government reports that aggressive driving habits such as rapid acceleration and aggressive braking can decrease fuel economy by as much as 33 percent. With mpg readings based on a full tank of gas, the effects that your driving style has on fuel economy are not so obvious. To see instantaneously how your driving impacts your overall gas mileage, you need a fuel economy meter: a gauge that displays mpg in real-time.
Watch How You Drive
Owners of cars with fuel consumption meters often notice that their gas mileage improves as a direct result of changing their driving style based on feedback from the fuel economy gauge. By adding an aftermarket mpg meter to your car, you can begin to see how a heavy foot on the gas and brake pedals sends your mpg readings way down. Conversely, you'll notice what driving habits increase your mpg.
Together, these visual indicators can change your driving habits for the better, increasing your average mpg while also saving you money and lowering your impact on the environment.
Hand It to the Hypermilers
Hypermilers, drivers who are obsessed with squeezing the most mpg possible from their vehicles, typically use fuel consumption meters to gauge the success of their extreme fuel economy efforts. And the vehicles they most favor, such as the Honda Insight and Toyota Prius, come with comprehensive fuel economy displays. But you don't have to buy a hybrid or be a hypermiler to improve your driving habits and save fuel. Adding an aftermarket mpg gauge to your vehicle will also do the trick.
Decades ago, vacuum-type gauges were introduced to give a relative display of fuel consumption based on the engine's manifold vacuum pressure. Newer momentum-based mpg meters use technology that senses the strength of your acceleration and braking and use simple red and green lights or gauges to indicate excessive or acceptable fuel consumption. Though they give you a relative sense of the impact your driving has on fuel economy, momentum-based gauges are not really the most accurate way to measure excessive fuel consumption.
Today's aftermarket digital fuel economy meters tap into the onboard diagnostic port (OBD II) found in all vehicles sold in the U.S. and Canada since 1996. Designed to allow service technicians to diagnose vehicle systems, the OBD II also provides a standardized means for aftermarket devices to access data from the vehicle's engine control module (ECM) to display numerous functions, including real-time mpg.
However, when shopping for a fuel economy gauge, be sure to check the manufacturers' Web sites to ensure that their products are compatible with your vehicle. Some meters are designed to work with all OBD II vehicles, while others are designed to work only with those that use a Controller Area Network (CAN) electrical system. The CAN protocol began to appear in new cars in 2003 and is now found on most new vehicles.
A Gaggle of Gauges
Auto Meter's Ecometer ($69.99) is a low-cost fuel economy gauge that uses the CAN protocol found on newer vehicles. It displays real-time fuel consumption in both a radial graph and an easy-to-read digital format. Four different modes are available to the driver, including average fuel economy, instant fuel economy and instant fuel economy with a digital tachometer or speedometer display.
Auterra's DashDyno SPD ($329.99) is a full-featured measurement and scanning device that works with any OBD II vehicle. In addition to displaying instant and average fuel economy, it can log data from engine sensors, measure horsepower and torque and even diagnose a "Check Engine" light.
The DashHawk ($299) from MSD Ignition is another full-featured measurement device that includes real-time fuel system status. It uses the CAN protocol and is available online as well as through MSD retailers.
PLX Devices offers three products geared toward fuel-conscious drivers. The original Kiwi ($299.99) is a full-featured meter that works with OBD II vehicles and incorporates "Green Driving" lessons to help you improve your fuel-sipping driving skills.
The company also recently introduced the Kiwi MPG ($89.99) that displays instantaneous mpg, trip mpg and dollars of gas consumed in an easy-to-read digital display. If you have an iPhone or iPod Touch, you can use the Kiwi WiFi ($149.99). It plugs into a car's OBD II and wirelessly connects to an iPhone or iPod Touch so it can send info to compatible auto-performance apps such as Rev by DevToaster and Dash Command by Palmer Performance Engineering.
The ScanGauge II ($169.95) from Linear Logic is popular among hypermilers and has been used to judge hypermiling competitions at events such as the MPG Challenge. The ScanGauge II is designed for all OBD II vehicles and displays any four of 12 built-in gauges at a time. Plus, it has a full-featured trip computer that logs 11 parameters and also functions as an OBD II error-code scanner to diagnose Check Engine lights.
Regardless of which fuel economy meter you choose, you'll likely be making your purchase online, as availability is limited at local auto parts retailers. Several of the meters mentioned above can be purchased directly from the companies' Web sites or through online retailers such as Amazon.com, Summit Racing and JC Whitney. ScanGauge also recently introduced a program with the AutoZone parts chain that allows you to special order the product and pick it up at a local AutoZone store.