Tests of physical vapour deposition (PVD) coatings performed in the past at NASA Glenn Research Center (GRC) in real fluid film bearing environment revealed inconsistencies in coating behaviour. Currently, a new lot of bearings with an improved diamond-like carbon (DLC) coating was tested. The oil-off tests revealed an improved coating performance for the new bearing lot than for previously-examined cases. In order to check the consistency in coating performance, bearings from the new lot ran 100 cumulative hours without oil-supply. Coating analyses before and after the tests in real fluid film bearing environment were performed at NASA GRC. Investigations were additionally conducted by means of an innovative indentation technique and related Finite element method simulations on the coatings of 2 of the bearings, one already tested in real-environment conditions and the other one new, at the Laboratory for Machine Tools and Manufacturing Engineering of the Aristotle University of Thessaloniki, Greece.