In highly-competitive markets, product quality is a critical element of sustainable development for manufacturing enterprises. The pursuit of quality is in essence a commitment to meeting the needs and expectations of customers. Firms often express customer needs in terms of quality characteristics in order to evaluate, monitor, and improve process performance. Reliability is an important quality characteristic. Specifically, reliability is the probability that a product will function as intended and will not malfunction within a certain period of time under certain operating conditions. Clearly, reliability influences the final evaluation made by customers of product quality. Since reliability is a time-oriented quality characteristic, it follows an exponential distribution. The performance standard for most quality indices is 1. To bring evaluation of reliability in line with convention, we propose ratio-based lifetime performance index (RLPI) . However, time-oriented data are continuous random variables, which implies that the observed values of the data are not precise. Furthermore, the performance of a product in various aspects inevitably declines over time. Clearly, longer product lifetime is not always better; it depends on the type of product. We therefore propose a two-tailed fuzzy statistical test for the RLPI to assist manufacturing enterprises in making more accurate evaluations of product reliability. An illustrative example is presented to demonstrate the practical applicability of our proposed approach.