How are you measuring this? A quick way to tell is to fill up your fuel tank with the box switched off (to do this please remove the fuse in the fuse link next to the battery) and make a note of the range. Re-insert the fuse, drive for 15-20 miles and you’ll see the range go up. When you next come to fill up you will see a much greater range. If you are still not seeing a saving, your box may not have been set up correctly - please complete the form below and we will check the unit has been installed correctly.