We investigated the positive bias temperature instability (PBTI) in 4H-SiC MOSFETs under a wide range of high oxide electric field (Eox) stress. The purpose of this study is to deepen the understanding of this phenomenon and experimentally evaluate the lifetime prediction model. For the first time, we analyzed the process of electron capture in SiO2 under high Eox stress by focusing on the region where electron capture is dominant and found systematical behavior of threshold voltage drift (ΔVth). Additionally, the amount of charges injected into the gate oxide (Qstress) was found to be a criterion for ΔVth in a high Eox region. Finally, it was presented that lifetime under PBTI testing exhibits a power-law relationship with Eox, resulting in longer lifetime than that predicted by the widely used E-model. Insights from the presented analyses must be beneficial for PBTI modeling and testing of SiC MOSFETs.