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Fuel Theft is Not Detected
  • technical_consulting
  • fuel
  • fuel_thefts

Fuel thefts are displayed in reports when the data received from the tracker meets all the theft detecting criteria. However, in some cases, the Fuel Thefts table doesn’t show the results, although you know for sure that fuel was stolen and can see a sharp drop in the Fuel level chart in the report. By following simple recommendations from this article, you can fix the situation and understand the logic of some fuel settings.

Possible causes and their elimination

Sometimes it will be enough to follow only one tip from the list below. More often, you will have to follow several recommendations at once. But in some cases, you won’t be able to avoid detailed analysis of all fuel level sensor settings, as well as of the features of incoming messages and parameters.

At the same time, fixing the situation with the displaying of one theft often results in the emergence of other inconsistencies in fuel reports. Thus, there should be a comprehensive approach to the fuel data analysis, considering not one theft but several at a time.

1. Theft is ignored due to smoothing

Try to reduce the filtration level in the fuel level sensor settings.


The fuel level in the tank fluctuates due to engine operation, acceleration, braking, turning, road bumps, vehicle tilt, and so on.

The higher the filtration level, the stronger is the smoothing used to compensate for FLS readings fluctuations. The stronger the smoothing, the easier it is to analyze the processed data, but the more distorted is the input information. Thus, to obtain the needed accuracy, you should set the filtration level to the minimum required. If the filtration level is too high, the processed data may no longer contain the fuel level difference corresponding to the theft. In most cases, it’s not recommended to use a filtration level higher than 10.

Often, test fuel drains are not displayed for this very reason: they are performed immediately after or before the filling, that’s why a short-term fuel level change is ignored due to smoothing. Actual thefts don’t assume the return of the fuel level to the previous state, so they will not be missed for the indicated reason.

You can also try enabling adaptive median filtration.

2. Theft is filtered by volume

Try to reduce the value of the Minimum fuel theft volume option in the fuel level sensor settings.


The 1% FLS accuracy declared by some manufacturers often doesn’t allow detecting small thefts in real conditions due to the fuel fluctuations in the tank mentioned above. That’s why it would be quite optimistic to set, for example, a 1-liter Minimum fuel theft volume right away. This option acts as a kind of coarse filter separating theft and normal fuel level fluctuations, which will remain even despite the use of filtration. Consequently, you should choose the Minimum fuel theft volume in proportion to the value of these fluctuations that in some cases can even reach 20 liters or more.

If you set a too high Minimum fuel theft volume, the actual theft may disappear from the report results.

3. Theft takes place during short stops

Try to reduce the Minimum stay timeout option to detect fuel theft in the fuel level sensor settings.


During a short stop, the fuel level can change significantly, therefore the analysis of short stops will result in detecting false thefts. Using the Minimum stay timeout to detect fuel theft option, you can configure the system to monitor thefts only during long stops and idle time.

If you set a too long Minimum stay timeout to detect fuel theft, then a long stop or idle time can be excluded from the analysis, and theft will not be registered.

4. Theft takes place in motion

Activate the Detect fuel theft in motion option in the fuel level sensor settings if the unit was actually moving at the moment of theft. Please note that in this case, in order to display the correct result, it’s recommended to enable the Time-based calculation of thefts.

Another method is to increase the minimum moving speed on the Trip Detector tab if the speed is not related to the actual trip of the unit but is related to the error in the initial data. However, if the speed in such messages is comparable to the speed of actual trips (for example, more than 10 km/h), you can probably delete such messages, and to avoid similar situations in the future, you can try to filter them out. Please keep in mind that you will not be able to recover messages deleted manually or as a result of message validity filtration, so pay special attention to these steps.


Speed determined by the tracker and displayed in the monitoring system doesn’t always clearly indicate that the unit is moving. This happens due to the inaccuracy of satellite navigation systems (GPS, GLONASS, and so on). To determine the fact of driving, the Min moving speed is used, which defines the minimum threshold of the speed value recognized by the system as a movement.

In rare cases, speed value inaccuracy reaches large values, which can be associated with both the tracker quality and the environment (terrain, being in a building, the presence of large metal structures nearby, and so on). Some trackers can independently mark messages with inaccurate speed as invalid. However, using Messages validity filtration, you can find and filter out such invalid messages already in Wialon. This filtration applies only to messages that arrive on the server after enabling the appropriate settings, that’s why you’ll have to delete previous invalid messages manually.

None of the variants work

You are probably faced with a more complicated situation than those discussed above, and you should contact technical support via support@gurtam.com. Make sure to indicate in your email the exact unit name, the report template name for verification, the minimum time interval for verification (for example, not a month, but several days), and other essential details.

Oleg Zharkovsky,Customer Service Engineer

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