If your in-cluster display (aka MFD) is displaying MPG numbers that are not accurate you can correct this and bring the MPG numbers closer to reality by adjusting the calibration number using VCDS.
To accomplish this adjustment you will need an OBD tool that can access the Adaptation values. We use the VCDS tool from Ross-Tech. This tool starts at just $199 and gives you access to all the control modules in your TDI. It is a must-have for anyone who performs their own maintenance or repairs.
After getting VCDS installed and running, plug the cable into your car’s OBDII port, turn on the vehicle’s ignition (do not start) and open VCDS.
Click the top-left “Select” button for selecting a control module on the opening screen.
Click on the button for “17-Instruments”
A new window will pop up and load the instruments module information. Click on the link for “Adaptation – 10”
A new window will pop up with a drop down menu for “Channel”. Open the drop down menu and look for IDE00499-Display correction of consumption and operating range. Should be close to the top – these are in numerical order FYI.
Once you click on the correct line, the display will update with stored values and enable you to enter a new value.
You will enter your new MPG calibration number into the “New Value” field in the form of a percentage. A higher percent will bring the display MPG down, a lower percent will bring the display MPG up. If you car is showing MPG numbers that are below what you are hand-calculating, you’ll want to set the correction number to under 100.
On this vehicle, the MFD was reading too high – it showed better MPGs than we were actually getting – so we increased the display correction from 105 to 108. Click on “Do It!” and then click “Yes” on the confirmation pop up.
You’re done. Remember to close out and quit VCDS completely before turning off the power to your car to avoid having any control module getting stuck.
Monitor your fuel economy over the next couple of weeks to see how your new calibration number matches what you are hand calculating. It will take a few tries to get it right, and we recommend waiting at least 3 tanks between readjustments.