Lewis harried Valtteri throughout the race, closing within 0.5s at one point before dropping back to secure second place.
"A great race, a great battle at the end of the season," said Lewis. "I did the best I could, but Valtteri did a great job - very clean and no mistakes.
"This is one of the harder tracks to overtake; you need to be 1.4 seconds faster than the car in front to overtake. I had a lot of pace in the second stint, but as soon as I got into that window of about 1.2 seconds, I was done. But it was neat that you could push all the way on the tyre, it didn't seem to drop off that much.
"It's really great for Valtteri to have this win, this is a real boost for him to go into the winter with.
"Now I'm looking forward to some time to sit down with my family and just reminisce about the whole year. It's been such a strong year, the team have been phenomenal all year long. I'm so grateful for everyone's hard work back at the factory and for all the support from Mercedes."