Solve kerner_task high CPU usage on El Capitan

After updating to El Capitan I noticed high CPU usage when doing anything mildly demanding on my MacBook Pro.

After spending some time investigating possible causes, starting in Safe Mode, disabling start item I managed to find the culprit: iStat menu.

The app has always been a trustworthy companion, but it hasn't been properly updated for the new OSX version.

So, before heading to the Genius bar, give this a shot