SAE Review of Dr. Schneider's Paper, Part 2

Effect of Lubricant Properties and Lubricant Degradation on Piston Ring and Cylinder Bore Wear in a Spark-Ignition Engine, Schneider et al:

First read part 1:
http://ferrarichat.com/forum/showthread.php?t=155439

Let me begin by saying again that every person interested in motor oil should go to SAE.org and purchase this article. (The paper was very detailed and I have tried to simplify the results. Also, I will need to report the results in several different postings so hang on please.) This research is made more relevant by actually using V-6 engines for wear testing - 1999 GM 3.4-L 60 degree block. And the radiotracer method of wear detection has been shown to be very accurate. They go on to say that cylinder wear and ring wear are perhaps the best areas to test oil and wear for engine longevity, particularly the rings.

Part 2:

Continuing with SJ GF-2 and SL GF-3 mineral based oils - they show that there is no significant differences between the oils for the initial break-in wear of top compression rings. They state that bore wear differes from ring wear in that most wear occurs during initial break-in and with start up periods. Steady state wear is very low except when changing to high load conditions. But even here bore wear is less than ring wear rates. They reiterated that start up wear was most significant but there were no differences between the oil classes.

They compared the mineral based SJ oils for wear rates by varying the ZDDP levels. There were no differences between phosphorous levels of 0.10 and 0.05. The only other level tested was zero ZDDP where wear rates doubled. Another SAE paper showed no difference in wear as long as the level was greater than 0.03 (1). They further show that there is in fact minimal bore wear differences when no ZDDP is present. (Note that doubling the wear rate is still not too bad as the rate of wear was still relatively low.) They conclude that the newer GF-4 oils will have no negative impact on ring and bore wear rates even with the reduced ZDDP levels.

(I heard information that the ZDDP levels will be 0.05 in the GF-5 Oils.)

Oil age effects were tested by measuring wear after the oil was subjected to 16,000 miles of city driving. Although the oils thickened some, TAN increased and TBN decreased, there were no differences in wear rates from fresh oil. The test oils were mineral based SJ GF-2.

aehaas

(1) Development of the Sequence III G Engine Oil Certification Test, Clark et al:
Engine tests were made more severe again. (Over the years the oil ratings have improved but this has always been despite the increase in testing severity. It was III ...D, E, F, and is now III G). The oil inlet temperature was decreased from 155 to 150 C. The test was 80 and is now 100 hours. There were 8 oil level adjustments allowed now there are 5. The inlet engine air temperature was raised from 27 to 35 C. The engine load was increased 25 percent.
Despite all this the current 0W-20 oils were still GF-4 compliant and showed minimal valve train wear characteristics as long as ZDP levels were higher than 0.03 percent. (The SM rated oils I have seen so far have levels of 0.08.)

Written with permission from Dr. Eric Schneider.