Axle Oil Aging – A Fresh Look at an Old Problem (Part One - Simplified Approach to Modeling)

Axle oil aging investigations are increasingly difficult. Oil drain extension programs have reached levels requiring years of testing for proper field validation. High temperature oxidation investigations used in the laboratory for development purpose are significantly faster, but always raise questions as they run at temperatures that do not represent normal operating conditions and where additive chemistries are no longer stable..

Long term stability investigations at 120°C with axle oil formulations have shown that most of them were significantly degraded in a relatively limited time span, despite the moderate temperature. The prime factor for axle oil aging appears to be thermal stability of the performance package rather than oxidation of the oil.

Laboratory thermal aging results at 120°C have given excellent correlation with field degradation in a long haul fleet test and product ranking in the lab was in line with industry expectations.

Simple calculations indicate that an algorithm using time and temperature is sufficient to predict long term aging, provided the equipment remains at reasonable temperatures during operation.