Transition metal borides (TMBs) represent a highly promising family of materials for functional coatings due to their abundance, cost-effectiveness, and exceptional mechanical properties. These include a high melting point, hardness of up to 60 GPa, excellent chemical and thermal conductivity, and outstanding resistance to wear. TMBs have distinct self-lubricating properties due to the formation of boron oxide, which helps to reduce friction. The temperature plays a significant role in the formation of boron oxide. However, the fundamental mechanisms behind this tribo-reaction are not yet fully understood, especially concerning TMB-based thin film materials. Understanding the oxidation behavior of physical vapor deposited TiB2±z and WB2±z thin films is essential for comprehending their friction and wear properties in high-temperature tribo contacts. Tribological tests reveal that sputter deposited super-stoichiometric TiB3.5 exhibits a significantly lower friction coefficient (~0.25), roughly half compared to that of sub-stoichiometric TiB1.67, tested at 500°C. This reduction is attributed to the higher oxidation rate of super-stoichiometric TiB3.5 and the presence of B-rich tissue phases at the column boundaries. Similarly, α-WB2±z coatings also exhibit self-lubrication properties. However, they tend to stabilize in the sub-stoichiometric form, resulting in reduced amounts of boron available for oxidation. Additionally, we conduct an in-situ investigation of the oxidation process in sub- and super-stoichiometric TiB2±z and WB2±z thin films using elastic backscattering spectrometry (EBS). This technique provides detailed depth profiles of the chemical composition over a temperature range from room temperature to 800°C. The oxidation data are further correlated with tribological, XPS, XRD, and TEM analyses, offering new insights into the lubrication mechanisms of boron oxide in TMB thin films across a wide temperature range.