A New Screen Test for the Thermal Oxidative Stability of Engine Oils - The Glass Panel Coker 2004-01-2024
Panel cokers have been used for a number of years for the evaluation of lubricant formulations with respect to thermal oxidative stability. There are, however, a number of drawbacks to the technique, particularly related to variability of the test and correlations to real engine performance. As a consequence of this, work has been undertaken to develop a new thermal oxidative screen test which provides greater flexibility and better correlation to engine tests. The glass panel coker test has been developed from a combination of several screen tests, and consists of a heated sump, where the lubricant is aerated and has NO2 additions, and from which oil is circulated over a high temperature metal surface.
The apparatus largely consists of standard laboratory glassware, and as such is easily customisable to incorporate additional features, for example simulated fuel or water dilution. This is therefore designed to mimic, in a simplified manner, the engine environment, where the fluid spends much of the time in the aerated, lower temperature sump, but is circulated through the hotter upper regions of the engine.
The test conditions have been developed through the use of a statistical surface response experimental design, in order to fully characterise the effects of all parameters on the severity of the test. This has allowed progress towards the tailoring of test conditions to enable suitable screening of a desired engine test. This test also results in the formation of a quantity of deposits on the hot metal surface, which are under further investigation and may form part of a future publication.