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Insights 10 min read

DIMO Insights #6: Fueling the Future: Discovering Refuel Events

September 25, 2023

Discovering Gas Refuel Events: What it Means for You as a Driver

Have you ever wondered how your car keeps track of how much fuel it has left in the tank? It turns out that the process is not as straightforward as you might think. In fact, it's based on a physical component floating inside your fuel tank, and it can be influenced by your vehicle's movement. But fear not, the DIMO Insights team has found a way to help drivers understand the fuel level in their car.

This can be used to help drivers identify refueling events, match to fuel prices per region and track their long-term spending on gas.

The Noisy Nature of Fuel Percent Remaining

The method your gas-powered vehicle uses to measure the remaining fuel is based on a physical device that floats in the fuel tank. This device moves as your vehicle moves, causing the liquid in the tank to slosh around. This motion can make the fuel percent remaining signal very noisy, which means it's not always accurate in reflecting how much fuel you have left.

To address this issue, we smooth this noisy signal using a technique called a Gaussian filter. Essentially, it averages the nearby values of the fuel percent reading with each individual value to create a smoother, more reliable series of readings.

Raw and Smoothed Fuel Percent Remaining Signal

Now, let's talk about what this research means for you as a driver. One of the key applications of this smoothed fuel percent signal is the automatic detection of gas refueling events. Here's how it works:

We roll a window through the smoothed fuel percent remaining data, calculating the difference between the last and first values within the window. This rolling window analysis helps identify the general timing of a refueling event.

Rolling Window through the Fuel Percent Remaining Signal

Derivative Estimation

To pinpoint the exact moment of a refueling event, the DIMO Insights team estimate the derivative (rate of change) of the smoothed fuel percent remaining signal. We look for the maximum value of the derivative, which indicates when the fuel percent remaining is increasing the fastest. This point is known as the inflection point and corresponds to the time of refueling.

Inflection Point During an Example Refuel Event

To validate these detected refueling events, we check if they align with known gas stations' locations. Ideally, the location of the inflection point should be within 100 meters of a gas station. If not, we compare the vehicle's stopping points with known gas station locations.

Example Discovered Refuel Events Near Known Gas Stations

We sum the estimated fuel added during these refueling events and multiply it by the EPA range of the vehicle. This helps ensure that the detected events are accurate. For example, if a vehicle added about 56.43 worth of fuel tanks in 110 detected refueling events, it should have driven around 24,829.2 miles, which is in line with the actual miles driven (24,120.3), though some refueling events may have been missed.

What Does this Mean for You as a Driver?

As a driver, this research can have several implications for you:

More Accurate Fuel Readings: The smoothing technique could lead to more accurate readings of your fuel remaining on the DIMO app, allowing you to better plan your refueling stops.

Fuel Efficiency Monitoring: DIMO can help you keep track of your vehicle's fuel efficiency by recording refueling events and the miles driven between them. This allows you to assess how changes in driving habits or vehicle maintenance affect your mileage and fuel consumption.

Expense Tracking: Easily monitoring refueling events on your phone enables you to maintain a detailed record of your fuel expenses. This can be particularly helpful for budget-conscious drivers who want to manage their transportation costs effectively. Further, historical refuel events can be matched to the average fuel price per region to help users understand their fuel costs over time.

Average US Fuel Prices per Region

In conclusion, the research on gas refuel events and signal smoothing is a promising development for drivers. It aims to provide you with a more accurate and reliable understanding of your vehicle's fuel status, leading to a smoother and more informed driving experience. So, the next time you hit the road, rest assured that your car's fuel gauge is working a little smarter, thanks to these advancements in technology.

Written by: Jeremy Lerner Senior Data Science Consultant

Jeremy Lerner is a Senior Data Scientist consulting with DIMO. He helped design Ford's BlueCruise and has published several papers and patents on how to utilize connected vehicle data to understand drivers and improve the driving experience. Data-driven simulations are Jeremy's natural playground.

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