Collection Level (CL) gives you an indication of how good your Car Collection is. You can increase your CL by adding new Cars to your collection, increasing their Star Rarity and by fitting Upgrades. Increase your CL to unlock new features and benefits.
Tap the helmet icon in the top-left corner of the Garage to view the details of your Collection Level.
How do I Increase my Collection Level?
You can increase your Collection Level by meeting the required amount of Collection Points for the next level. Collection Points are earned whenever you successfully unlock new Cars, increase your Cars' Star Rarity, and upgrade your Cars.
You will also get Milestone rewards as your Collection Level increases.