Mercedes boss Toto Wolff says the manufacturer will face its toughest challenge in 2016, amid an expected threat from Ferrari.
Mercedes has dominated Formula 1 since the introduction of 1.6 litre v6 power units at the start of 2014 but has faced an increased threat from Ferrari, which has claimed three victories in 2015.
"We go to Abu Dhabi with the best possible Championship positions secured and a chance to reflect on an incredible year," he explained.
"We can all be extremely proud of what we have achieved in 2015. To raise the bar from 2014 was always going to be a huge challenge - but everybody at Brackley, Brixworth and Stuttgart has taken on that challenge exceptionally well.
"While we celebrate a job well done this time around, however, the next challenge will be upon us before we know it. 2016 will undoubtedly provide our biggest test yet as a group.
"We will not be backing off - and an entertaining battle at the front between our boys for one last time in 2015 will be the ideal way to show that."