Originally Posted By: CATERHAM
JAG, I agree. I actually pointed that out to ekpolk in his recent post "How-Le-Cow 0W-20 forever" with NOACK at 14% for 0W-20 PP. PP 5W-20 is not much better at 13.2% and even PP 5W-30 at 12.5 is not great.
I'd posit though, that if the oil temp's are kept down; say 100C or less, volitility is less of an issue. It doesn't appear to be an issue in most UAO's i.e., a vis or oil consumption increase.
Besides, 20 wt is not suitable in most higher temp applications anyway.
Two thoughts here. First, yes, the Noack number for the 20 wt PP oils look awful on paper. And yet, in actual real-world service, they don't seem to have an impact. If this were a "real" issue, I'd expect to see a pattern in the UOA, or perhaps reports of excessive consumption, thickening, or both. But there does not appear to be such a pattern. Still, the numbers are what they are (assuming they're legit, and why would an oil maker "overrate" a Noack number...?). I guess that my engine is pretty safe, as I'm constantly roaring around at 80-ish mph in the Florida summer heat, and if I'm having any boil-off, it's minimal enough that I really can't see it. On my first run of PP 0w-20, 5k miles (right before the GC experiment), the oil level might have been a millimeter lower on the stick at the end of the OCI, compared to the beginning, but absolutely nothing dramatic.
Second, I really don't think this "not suitable for high temp applications" thing is a problem for "normal" drivers (as opposed to track or other racing use). The highest coolant temp I've ever seen on my SG-II is 207F (Camry). The vast majority of the time, no matter how hot it is outside, the temp cycles around 190F. If an engine simply DOES NOT reach any temp near those which would challenge ANY grade of oil, is this really an issue to worry about?
