To improve the efficiency in non-conformal type of machine elements, it is of crucial importance to gain knowledge about the underlying mechanism that governs the formation of an elastohydrodynamic (EHD) oil film. This study was set out to explore the dependency of surface roughness and operating conditions on the transition to full film elastohydrodynamic lubrication (EHL). A ball-on-disc device, arranged for monitoring electrical contact resistance (ECR), was operated under a wide variety of heavily loaded rolling/sliding conditions. To reduce complexity in the film formation process, any tribo-chemical effects were minimized by the selection of a neat synthetic lubricant. Two types of tests were set-up to examine, in particularly, the role of load and slide-to-roll ratio (SRR) on the EHD film formation. In the first, the contact was mapped over the speed and SRR parameter space to capture the transition from EHL to mixed lubrication when starting in EHL. The contact was then operated under different loads to reveal the EHL transitions dependency to variations in Hertzian contact pressure. In the second set of tests, the contact was initiated in mixed lubrication, and film formation was monitored until surfaces achieved lift-off for EHL by adequate surface modification due to running-in. Subsequently, special emphasis was set out to investigate what transformations those surfaces had to undergo in order for EHL lift-off to take place.