Real World Fleet Test to Determine the Impact of Lower Viscosity Engine Oils from Heavy-Duty CNG and Diesel Buses. Part II: Oil Performance 2017-01-2351

Low viscosity engine oils are considered a feasible solution for improving fuel economy in internal combustion engines (ICE). So, the aim of this study was to verify experimentally the performance of low viscosity engine oils regarding their degradation process and possible related engine wear, since the use of low viscosity engine oils could imply higher degradation rates and/or unwanted wear performance. Potential higher wear could result in a reduction in life cycle for the ICE, and higher degradation rates would be translated in a reduction of the oil drain period, both of them non-desired effects. In addition, currently limited data are available regarding “real-world” performance of low viscosity engine oils in a real service fleet.

In this particular case, there were included out-of-the European Automobile Manufacturers' Association (ACEA) oil specifications in terms of HTHS dynamic viscosity, where low viscosity was considered (3.0 mPa·s), making this test highly interesting for industry. On this test, 49 buses were monitored using a deep and extensive oil analysis program, comprising two engine technologies (Diesel and CNG), four engine types and three different lubricants, two of them low viscosity engine oils and other two as a reference baseline, during an oil drain period of 30000 km, taking between 5 to 10 samples per bus.

For every sample, a broad list of thermo-physical and chemical properties were measured, and specially engine wear was quantified using ICP-OES, in order to detect abnormal wear patterns in the engine.

Results indicate that oil performance and wear effects do not show abnormal patterns due to use of low viscosity engine oils, even some parameters obtain a better performance because of higher quality formulation.