I was asked to review this article. I have purchased the article and here is my review:
Properties of Engine Bearings Lubricated with Low HTHS Viscosity Oils, Ono et al: Presented SAE oil Congress Detroit Feb., 1998, SAE 980702:
Tests were performed using experimental paraffin mineral based oils with SG, API rated additives. The 100 C k. viscosities were 5.6 to 10.6, HTHS was 1.8 to 3.0. Engine testing was done at 4,800 and 6,500 RPM with sump oil temperatures at 150 C and thermocouple monitored bearing temperatures at 180 C.
They concluded that the minimum oil film thickness needed to get “normal” wear was 1.4 - 1.6 micrometers. The Minimum HTHS at 150 C needed was 2.4 to 2.6. I also noted that the wear decreased with tighter bearings (less clearance) for the oils.
Whereas main bearing wear increased with the viscosity below 2.2 HTHS, the con-rod bearing showed virtually no wear at the lowest tested 1.8 oil. Of the 3 bearings types tested 2 showed minimal wear and only one was adversely affected by HTHS viscosity below 2.2.
Critical analysis:
The testing is over 8 years old now with SG, SH, SJ, SL oils by the wayside. If HTHS of 2.4 resulted in minimal wear ( in some bearings) with those experimental oils, what would the result be using today’s oils?
The test temperatures and RPM's were among the most severe. What would the test show, even back then, if the sump was kept at say 120 C. Also, the bearing temperatures were kept high artificially, to combat the additional cooling encountered with the thinner oils. All other things kept constant, wear increases with engine temperature.
How would modern, thin synthetic oils, perform in the same test? What would the test show if fully formulated SG oils were used instead of the experimental oils?
I thought it was a good paper but my conclusions are that thin oils today, especially synthetic oils, are not only safe, but preferred.
aehaas
Properties of Engine Bearings Lubricated with Low HTHS Viscosity Oils, Ono et al: Presented SAE oil Congress Detroit Feb., 1998, SAE 980702:
Tests were performed using experimental paraffin mineral based oils with SG, API rated additives. The 100 C k. viscosities were 5.6 to 10.6, HTHS was 1.8 to 3.0. Engine testing was done at 4,800 and 6,500 RPM with sump oil temperatures at 150 C and thermocouple monitored bearing temperatures at 180 C.
They concluded that the minimum oil film thickness needed to get “normal” wear was 1.4 - 1.6 micrometers. The Minimum HTHS at 150 C needed was 2.4 to 2.6. I also noted that the wear decreased with tighter bearings (less clearance) for the oils.
Whereas main bearing wear increased with the viscosity below 2.2 HTHS, the con-rod bearing showed virtually no wear at the lowest tested 1.8 oil. Of the 3 bearings types tested 2 showed minimal wear and only one was adversely affected by HTHS viscosity below 2.2.
Critical analysis:
The testing is over 8 years old now with SG, SH, SJ, SL oils by the wayside. If HTHS of 2.4 resulted in minimal wear ( in some bearings) with those experimental oils, what would the result be using today’s oils?
The test temperatures and RPM's were among the most severe. What would the test show, even back then, if the sump was kept at say 120 C. Also, the bearing temperatures were kept high artificially, to combat the additional cooling encountered with the thinner oils. All other things kept constant, wear increases with engine temperature.
How would modern, thin synthetic oils, perform in the same test? What would the test show if fully formulated SG oils were used instead of the experimental oils?
I thought it was a good paper but my conclusions are that thin oils today, especially synthetic oils, are not only safe, but preferred.
aehaas
art 1, Sagawa et al:
