Ground-breaking technologies and innovative design of upcoming vehicles introduce complex maintenance procedures for auto mechanics. In order to present these procedures in an intuitive manner, the Mobile Augmented Reality Technical Assistance (MARTA) project was initiated. The goal was to create an Augmented Reality-aided application running on a tablet computer, which shows maintenance instructions superimposed on a live video feed of the car. Robust image-based tracking of specular surfaces using both edge and texture features as well as the software framework are the most important aspects of the project, which are presented here. The resulting application is deployed and used productively to support maintenance of the Volkswagen XL1 vehicle across the world.