Engine Oil Analysis sebagai Langkah Predictive Maintenance pada Bus Rapid Transit Transjakarta Scania K320IA 6x2 CNG Euro VI Studi Kasus: Customized Maintenance Contract (CMC) antara PT. United Tractors dengan PT. Mayasari Bakti = Engine Oil Analysis as a Predictive Maintenance Measure on Transjakarta Scania K320IA 6x2 CNG Euro VI Rapid Transit Bus Case Study: Customized Maintenance Contract (CMC) between PT. United Tractors with PT. Mayasari Bakti