Well, I thought some data might be useful to support some of the discussions going on in the 10W-60 v. 5W-30 Thread. I had an oil sample analyzed by Blackstone Labs in April 2005.
2/2000 M5; 57,250 total miles at time of oil change; 6,100 miles on the oil; .75 liter oil added during interval with weekly checks.
Air temperature range (in SC) during the interval was probably 85F to 35F, but the average air temp while operating is probably around 50F to 60F. I usually run trips of less than 10 miles under light duty conditions. Minimal Highway miles as a % of the whole. Weekly "fun drives" in the rural/mountain areas provide a rigorous work out for the engine routinely.
Key Points of the Results:
1) TBN was 2.0 - so additive package still OK
2) Aluminum - 9ppm (midly high relative to their data set avg. of 5ppm*)
3) Lead - 7ppm (midly high relative to their data set avg. of 4ppm*)
4) SUS Viscosity @ 210F - 86.3 (values should be 87-98 according to Blackstone)
5) Flashpoint - 355 (values should be >375 according to Blackstone)
6) Fuel % - 1.0% (values should be <1.0 according to Blackstone)
*Average oil sample for this type of engine had 3,500 miles on it in Blackstone's data. Their reporting does not compensate for my sample's 6,100 mile interval from the average 3,500 mile interval, so direct comparisons of wear metals by ppm are suspect)
My take aways were that I might need to reduce the oil change interval to manage what seems to be a fair amount of fuel making it into the oil. This may be the primary factor adversely affecting viscosity. If the % fuel in oil is a problem, I'm not sure if the cause for that was lower temps in the winter on short trips, or just the short, light-duty trips. I guess we'll see at my next change this summer.
:cheers:
2/2000 M5; 57,250 total miles at time of oil change; 6,100 miles on the oil; .75 liter oil added during interval with weekly checks.
Air temperature range (in SC) during the interval was probably 85F to 35F, but the average air temp while operating is probably around 50F to 60F. I usually run trips of less than 10 miles under light duty conditions. Minimal Highway miles as a % of the whole. Weekly "fun drives" in the rural/mountain areas provide a rigorous work out for the engine routinely.
Key Points of the Results:
1) TBN was 2.0 - so additive package still OK
2) Aluminum - 9ppm (midly high relative to their data set avg. of 5ppm*)
3) Lead - 7ppm (midly high relative to their data set avg. of 4ppm*)
4) SUS Viscosity @ 210F - 86.3 (values should be 87-98 according to Blackstone)
5) Flashpoint - 355 (values should be >375 according to Blackstone)
6) Fuel % - 1.0% (values should be <1.0 according to Blackstone)
*Average oil sample for this type of engine had 3,500 miles on it in Blackstone's data. Their reporting does not compensate for my sample's 6,100 mile interval from the average 3,500 mile interval, so direct comparisons of wear metals by ppm are suspect)
My take aways were that I might need to reduce the oil change interval to manage what seems to be a fair amount of fuel making it into the oil. This may be the primary factor adversely affecting viscosity. If the % fuel in oil is a problem, I'm not sure if the cause for that was lower temps in the winter on short trips, or just the short, light-duty trips. I guess we'll see at my next change this summer.
:cheers: