The automobile warranty period is developing towards long-term warranty direction (160000 km or 10 years), and about 50% of car registrations within 10 years are eliminated. Due to this, information on discarded cars for reasons like obsolescence or outdated need to be considered while estimating the lifetime characteristic in the reliability assessment. Owing to setting of the long-term warranty period, valuable failure data in the market can be easily obtained. In this context, the more frequently the automobile is used, the more the failure opportunity is, and so the method of estimating the lifetime by taking the failure data as the overall usage time distribution may result in wrong estimated result, which should be considered. In this study, we only take the failure data within the warranty period as the object to build the model using the discard time distribution and the failure time distribution and the censoring time distribution. As a result, we proposed a method for improving the lifetime characteristic's estimation precision with information on discarding.