Sylvie Willis
Many modern cars have real-time fuel-economy readouts on the instrument panel, but what about older vehicles? There are several aftermarket devices that can be added to a car to display fuel consumption, such as the MPGuino, an Arduino-based fuel consumption display/trip computer, or the Scangauge II, the most popular mpg gauge on the market. These devices can help drivers save gas, money, and the environment. However, some in-dash trip computers that show fuel economy can be inaccurate, so it's important to do your research before choosing a device.
| Characteristics | Values |
|---|---|
| Fuel consumption gauge | Can be added to a car |
| Fuel consumption gauge options | MPGuino, Scangauge II, Dashhawk, Bully Dog Technologies' Watchdog, Kiwi, AccuFuel for the iPhone, Vacuum gauge |
| MPGuino | Costs $30-40 to put together, completely DIY, works with almost any electronically fuel-injected vehicle |
| Scangauge II | Most popular mpg gauge |
| Dashhawk | $300, works with 96+ vehicles |
| Bully Dog Technologies' Watchdog | Can be used as a performance gauge of 20+ items, can be used as a performance tool for optimizing driving habits |
| Kiwi | Works with 96+ vehicles |
| AccuFuel for the iPhone | Allows you to record fill-ups and calculates gas mileage |
| Vacuum gauge | Simple mechanical gauge, hooked into the manifold with some tubing, costs under $50 |
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What You'll Learn
DIY options for adding a fuel consumption gauge
There are several DIY options for adding a fuel consumption gauge to your car. Firstly, it is important to note that some newer cars have real-time fuel-economy readouts on the instrument panel. If your car has this feature, you can simply set the display to instant mileage and pay attention to your driving habits to improve fuel economy.
If your car does not have this feature, there are a few gadgets and methods you can use to add a fuel consumption gauge. Here are some options:
Vacuum Gauge
One DIY method is to install a vacuum gauge, which has been used by drivers since the 1940s and 1950s to improve fuel economy. The vacuum gauge is a simple mechanical device that can be purchased for under $50 and hooked into the manifold with tubing. It measures the manifold vacuum pressure, which is inversely proportional to throttle position; the higher the manifold vacuum pressure, the better the fuel economy. The gauge acts as a feedback system, immediately informing the driver if their driving habits are resulting in good or bad fuel mileage. It can be installed anywhere on the dashboard, preferably in plain view. The hardest part of the installation is finding a hole through the firewall to route the hose. However, it's important to note that vacuum gauges don't work on diesel engines, which have no throttle blades and, therefore, no manifold vacuum.
MPGuino
The MPGuino is another DIY option that can be configured to work with almost any electronically fuel-injected vehicle. It costs around $30-40 to put together, but it requires soldering and wiring skills. It is open-source and one of the few options for pre-1996 vehicles.
Scangauge II
The Scangauge II is a popular mpg gauge that is easy to install; simply plug it into your OBDII port under the dash. It has a backlit display that shows four pieces of data at once and can check engine codes and aid in other diagnostics.
Smartphone Applications
There are also smartphone applications, such as AccuFuel for the iPhone, that allow you to record fill-ups and calculate gas mileage.
Other DIY Projects
There are various other DIY projects and gadgets available to add a fuel consumption gauge. Some involve using sensors, such as magnetic sensors or fluid flux sensors, to measure fuel consumption and miles travelled. Others use software and coding to transform signals into distance travelled and gasoline used. It is important to do your research and consult reliable sources and experts before attempting any DIY project on your vehicle.
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Aftermarket devices that can be added to a car
There are several aftermarket devices that can be added to a car to monitor fuel consumption and improve fuel economy. Here are some options:
- The MPGuino is a DIY device that can be configured to work with almost any electronically fuel-injected vehicle. It costs around $30-40 to put together, but it requires soldering and wiring knowledge.
- The Scangauge II is a popular mpg gauge that can be used to monitor fuel consumption.
- The Dashhawk is a display from MSD that works similarly to the Scangauge but comes with a $300 price tag.
- The Watchdog from Bully Dog Technologies is another device that can be used as a performance gauge for 20+ items and a tool for optimising driving habits.
- A vacuum gauge is a simple mechanical gauge that can be hooked into the manifold of a car with some tubing. It measures the vacuum pressure in the intake manifold, which is related to fuel consumption. This option is not suitable for diesel engines.
- AccuFuel for the iPhone allows you to record fill-ups and calculates gas mileage.
It is important to note that some vehicles with trip computers that show fuel economy on the dash can be inaccurate, so it is recommended to rely on manual calculations for accurate comparisons. Additionally, some gadgets and potions sold online that claim to improve fuel economy may not be effective.
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How a real-time fuel consumption display works
Real-time fuel consumption displays are becoming increasingly common in newer vehicles, driven by consumer demand. Automakers are starting to add mpg displays to their vehicles, but there are also many third-party devices that can be added to a car to display this information.
Real-time fuel consumption displays work by calculating the amount of fuel being injected into the engine cylinders. This is known as the injector pulse width or duty cycle. The longer the injectors are open, the more fuel they inject. This data is used to calculate the instantaneous fuel consumption, which is updated every few seconds. The display will also show the overall average fuel consumption since the last reset, and often a moving average fuel consumption over a longer period.
Devices that can be added to a car
There are several devices that can be added to a car to display real-time fuel consumption. One popular option is the Scangauge II, which can be plugged into the On Board Diagnostic System (OBD II) port under the dashboard of most post-1996 cars and light trucks. The MPGuino is another option, which is an Arduino-based fuel consumption display that can be configured to work with most electronically fuel-injected vehicles. It is a DIY solution that requires soldering and wiring knowledge, but it is a low-cost option at around $30-40. The Dashhawk is another display that works in a similar way to the Scangauge but comes with a $300 price tag.
Benefits of real-time fuel consumption displays
Real-time fuel consumption displays can be incredibly useful for drivers who want to improve their fuel economy. By providing immediate feedback on how their driving style affects fuel consumption, drivers can make small adjustments to their driving habits to achieve higher fuel economy.
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In-built fuel consumption displays in newer cars
In-built fuel consumption displays, also known as instant MPG readouts, are becoming more common in newer cars. These displays give drivers real-time information on their miles per gallon, allowing them to see exactly how much fuel they are using at any given moment. This can help drivers improve their fuel economy by making simple changes to their driving habits, such as easing up on the accelerator or braking more gently.
While some cars have fuel economy gauges that show the average fuel economy over time, instant MPG readouts provide a more detailed and immediate understanding of fuel consumption. These readouts use sensors to measure various factors, including the car's engine speed, fuel flow rate, manifold pressure, and throttle position. The data is then fed into a computer that calculates and displays the instant MPG result.
Instant MPG readouts are particularly popular among "hypermilers", who are drivers obsessed with maximising their fuel economy. Certain car models, such as the Honda Insight and Toyota Prius, are favoured by hypermilers for their comprehensive fuel economy displays. Additionally, most hybrid cars now come equipped with instant MPG readouts as standard.
For older cars or vehicles without built-in fuel consumption displays, there are aftermarket options available. These include devices such as the Scangauge II, the MPGuino, and the Auto Meter's Ecometer, which can be installed in compatible vehicles to provide real-time fuel consumption data. These devices can be a great way to improve fuel efficiency and save money on gas, but it's important to ensure compatibility before purchasing.
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The accuracy of fuel consumption displays
The "miles-to-empty" display, also known as the range estimation, is affected by the vehicle's most recent driving conditions. For example, when driving conditions change, such as transitioning from city driving to highway driving, the estimation may lose accuracy until it adjusts to the new conditions. Similarly, the accuracy of the display can vary over short distances, even if it is accurate over longer distances.
The AAA (American Automobile Association) has tested the accuracy of in-vehicle fuel systems that measure fuel economy and range. They found that while the systems were collectively relatively accurate, a closer examination of different driving scenarios revealed significant variability based on changes in speed, acceleration, and distance. Drivers should not overly rely on these displays, as they are not perfect, and running a vehicle to the last drop based on the display may cause the vehicle to sputter out sooner than expected.
To avoid running out of fuel, AAA recommends that drivers fill up when their tank reaches a quarter full. This will help prevent unexpected delays and reduce the risk of fuel pump damage caused by regularly running the vehicle's gas tank to empty. Additionally, drivers can maximize fuel economy by avoiding hard acceleration, inflating tires to the recommended pressure, removing unnecessary bulky items, and minimizing the use of roof racks and special carriers.
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Frequently asked questions
Yes, you can add a fuel consumption gauge to your car. There are several gadgets available that can be retrofitted to your car to help save gas. For example, the MPGuino is an open-source option that can be configured to work with almost any electronically fuel-injected vehicle. It is a DIY option, so you will need to know how to solder and wire it into your car. Other options include the Scangauge II, the Dashhawk, and the Watchdog from Bully Dog Technologies.
A fuel consumption gauge typically works by monitoring the fuel line and odometer data at periodic intervals and displaying the elapsed mileage divided by the cumulative amount of fuel used. This can be done by monitoring the amount of fuel being injected at any one time or by measuring the injector pulse width or duty cycle. The interval of reporting can be based on time, such as every few seconds, or by distance, such as every 700 feet traveled.
Yes, there are alternative ways to improve fuel economy without adding a fuel consumption gauge. For example, you can use a vacuum gauge, which is a simple mechanical gauge hooked into the manifold with tubing. However, this will not work on diesel engines. You can also use smartphone applications, such as AccuFuel for the iPhone, which allows you to record fill-ups and calculate gas mileage.
