Hybrid Operation Characteristics and Their Impact on Engine Oil Requirements

With the increasing regulatory stringency on emission reduction and efficiency improvement, the automotive industry has experienced a significant shift in the hardware platform. Among all the technology candidates, hybrid technology is still considered one of the most viable approaches to meet the regulation requirement (both emission and efficiency) at an affordable cost to both the customer and the manufacturer. Indeed, the development of internal combustion engines (ICE) has lasted over 100 years. But for the application in a hybrid platform, new engine operating characteristics are expected, resulting in different performance requirements for engine oils.

Therefore, it is crucial to understand these characteristics of a hybrid engine, from which the insights of fluid requirements can be derived.

We selected different kinds of hybrid platforms to characterize hybrid operation in this work.

Various driving cycles have been utilized to evaluate the engine operation of those hybrid platforms. The hybrid operation has been well characterized by thoroughly analyzing engine parameters and emission data. The fluid temperature was recorded while vehicles were run over those cycles. The temperature profile was examined to illustrate the impact of the driving cycle and hybrid platform on fluid properties. It was found that the driving cycle is a very effective tool to deepen the technical understanding of the interactive operation between ICE and battery in a hybrid powertrain. That interactive operation will ultimately determine the engine performance and fluid working environment.

Based on the knowledge and insights from vehicle testing, engine testing was designed to accelerate the oil dilution process. We can investigate the impact of different operating parameters on oil dilution through a series of engine testing under various operating conditions. Detailed oil analysis was conducted for those samples collected from engine tests. The analytic results indicate that the oil samples generated from the engine test cover a wide range of dilution levels, representing the oil samples found in a real-world application. Moreover, the analytic results of those samples collected periodically during the testing prove that we can simulate the oil dilution process on an engine bench.