Passive testing is an approach to verify system behavior by observing logs from normal operation, without actively injecting test stimuli. This paper presents an industrial case study of applying passive testing in the domain of vehicular embedded systems, utilizing two specialized tools: Timed Easy Approach to Requirements Syntax (T-EARS) for specifying temporal requirements, and Napkin Studio for evaluating these requirements against real system execution logs. We collaborated with Volvo Construction Equipment (VCE) to translate a set of natural language requirements into structured T-EARS specifications. Then we used Napkin Studio to test these requirements against recorded machine log data passively. We evaluate the feasibility of this approach, the extent to which it can detect requirement violations or injected faults, and the perceptions of industry stakeholders regarding the adoption of such passive tests in their verification process. The results show that a majority of functional requirements can be expressed as Guarded Assertions (GAs) and validated on logs, uncovering specific issues. Stakeholders found the method promising for improving test coverage and efficiency, although integration challenges (e.g., log signal inconsistencies and tool usability issues) were noted. Overall, this work provides empirical evidence that passive testing with T-EARS and Napkin Studio can complement traditional hardware-in-the-loop testing, offering a scalable and non-intrusive verification approach in developing vehicular systems.