Sliding slightly off topic:
A & C I've been thinking about using multigrade oil once my rapidly dwindling stock of 100W is finished. I have been led to believe that they provide better protection to engines that stand for a while (mine can be idle for at least a month at a time). What concerns me is that they might not be appropriate and / or approved for an ancient engine like a Cirrus Minor II with it's oil flinger front crank seal and ancient design oil seals.
Hopefully I am avoiding the spalling effect caused by overly viscous cool oil as I wait until the oil temp needle is off the stop (100F / 40C) before giving the engine any welly. However, I have seen my oil temp getting up to 180F during the summer when I was in a fast, for an Auster, cruise. I was surprised at how long it took for the oil to cool down to a more normal 150-160F after reducing the power. Would a multi grade help in these circumstances?