Online consumer reviews provide an important source of information for automobile purchase decisions, yet relatively little is known about the informational value of cumulative electronic word-of-mouth (eWOM) ratings that reflect long-term online reputation. This study examines whether cumulative eWOM ratings are associated with subsequent automobile sales and explores their relationship with subsequent changes in monthly ratings and rating entropy. We combine monthly automobile sales data from Chezhu Zhijia with more than one million individual consumer reviews collected from Autohome between January 2013 and December 2025. Review-level data are aggregated to the automobile model-month level to construct cumulative eWOM measures, and the hypotheses are examined using two-way fixed-effects models. The results show that cumulative eWOM ratings are positively associated with subsequent automobile sales. Higher cumulative ratings are also associated with more favorable changes in subsequent monthly ratings and lower rating entropy. The positive association between cumulative eWOM ratings and automobile sales becomes stronger as product age increases and varies with cumulative rating entropy. These findings remain qualitatively unchanged across a broad set of robustness and additional analyses. This study highlights the informational value of cumulative online reputation for high-involvement durable goods and provides new evidence on the conditions under which accumulated consumer evaluations are associated with market outcomes.