I got the dealer to give me the report of what was done after the car was sold to them a few months ago and I see that X0-5W20-QSP was used - synthetic blend but 5W20. Would it be wise to switch out for 0W20 esp given the unusually cold weather here in DC, now? ...
I don't see an opportunity for life extension; your "unusually cold" is my normal, and I've been doing oil analyses all along. February 2015 was record cold and there's nothing odd resulting.
From this data, I would suggest against 0W20 oil. Look at the "flashpoint" and "fuel%" and it appears 0W20 lets more fuel into the oil. Conversely, for the last change, I had a 3+ hr. highway run immediately preceding, which would have driven any fuel from the oil. I'll let you know about the 5W20 EP late this year.
Note that I also list the base oil contents at right, for comparison. Many of the additives vary with the oil, not the service.
I doubt using blends, full synthetic or different viscosity oils will have any significant effect on engine life. The general benefit of using lower viscosity oil in cold weather is the engine will "turn" easier and thus there should be a FE benefit when the engine is cold. The general benefit of using synthetic oil is that one can go longer between oil changes.
I would use 0W20 full synthetic. If you really want to get into a debate on oil go to BOB IS THE OIL GUY website.
+1 to Bob
Based on my car's data, I'm hypothesizing that in hybrids running primarily "city" mode, where the engine is off much of the time and oil never gets to operating temperature, 5W20 may have greater resistance to oil infiltration. Note that my car's only winter oil change was 2014, also the only winter I stayed warm taking the highway nearly every day. It's the lowest flashpoint with 5W20. I await the next oil change result to see if there's a consistent pattern. No reason to expect one; most 5W20 synthetics are real close to 0W20 viscosity specs.
When the oil life alarm next sounds, I may just test, not change, and see if my oil ages as well as Paul's has... with TBN, too.
Edited by fbov, 08 January 2018 - 10:08 PM.