Individually, none of these UOA's is particularly interesting. My confusion is between test 2 and 3 which was the exact same sump of 50% PP 5W-20 and 50% PP 5W-30, all D1G2.
Test 2 was after apx. 6 months of mostly typical short-trip driving - 2 or 3 or 4 miles per trip. Sometimes even 10 miles per trip.
Test 3 was after a four-day road trip and was taken immediately after the 210 mile drive home with 2 intermediate 10 minute stops. (The purpose of he test was to see if fuel dilution would decrease with a lengthy drive.)
Otherwise, the same protocols were used for both tests.
One of the things that confuses me between test 2 and test 3 is the difference in reported levels of magnesium, phosphorus and zinc. Depending on which way you cypher it, there is a reported difference of between 13% and 18% in these elements. Seems to be outside of an acceptable margin of error to me. I would tend not to be concerned about something less than 10%, but maybe I am overly optimistic. Any thoughts?
More confusing is the viscosity reading of test 3. When virgin my 50/50 mixture should have been somewhere in the 9.2 cSt @ 100°C based on typical viscosities from the data sheets. Test 2 with 3.4% fuel seems to be in the realm of a correct viscosity at 7.8. If my 210 mile trip did in fact evaporate enough fuel to warrant a 2.3% level (I am skeptical) I would venture to estimate the viscosity should have been somewhere around 8.2 to 8.3, not the 9.2 reported. I am at a loss to fathom how oxidative thickening or some other phenomenon could have increased the viscosity that much over that little time and usage. What could I be missing?
Test 2 was after apx. 6 months of mostly typical short-trip driving - 2 or 3 or 4 miles per trip. Sometimes even 10 miles per trip.
Test 3 was after a four-day road trip and was taken immediately after the 210 mile drive home with 2 intermediate 10 minute stops. (The purpose of he test was to see if fuel dilution would decrease with a lengthy drive.)
Otherwise, the same protocols were used for both tests.
One of the things that confuses me between test 2 and test 3 is the difference in reported levels of magnesium, phosphorus and zinc. Depending on which way you cypher it, there is a reported difference of between 13% and 18% in these elements. Seems to be outside of an acceptable margin of error to me. I would tend not to be concerned about something less than 10%, but maybe I am overly optimistic. Any thoughts?
More confusing is the viscosity reading of test 3. When virgin my 50/50 mixture should have been somewhere in the 9.2 cSt @ 100°C based on typical viscosities from the data sheets. Test 2 with 3.4% fuel seems to be in the realm of a correct viscosity at 7.8. If my 210 mile trip did in fact evaporate enough fuel to warrant a 2.3% level (I am skeptical) I would venture to estimate the viscosity should have been somewhere around 8.2 to 8.3, not the 9.2 reported. I am at a loss to fathom how oxidative thickening or some other phenomenon could have increased the viscosity that much over that little time and usage. What could I be missing?
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