The majority of bearings in the world are lubricated by grease, and nearly 80% of premature bearing damage is attributed to lubrication issues. Accurate measurement and prediction of film thickness are crucial aspects of understanding the lubrication mechanism in grease-lubricated bearings. This work focuses on grease film thickness measurement using the capacitance method in real bearings. It comprehensively reviews the current status, identifies key challenges, and proposes solutions. Mechanisms of mainstream electronic components in capacitance measurement were reviewed for the first time. It enables more accurate capacitance measurement. A new capacitive model and electric network to measure film thickness in fully flooded, starved, and mixed regimes are developed. It is more comprehensive compared to current models. Classic dielectric models are reviewed, and suitable ones for lubricants are proposed. It facilitates a more precise film thickness measurement. Finally, a new grease film thickness model (bearing raceway) is proposed based on the 113 literature capacitive film thickness data points from five different authors. The satisfied R-squared value indicates a strong correlation.