Patman,
I want to add a data point or two to the thick/thin debate is all.
I've got meticulous mileage records on 10W and 15W-40 in this car, and want to see the effects mileage wise of the thickest oil that I was comfortable with, along with the thinnest.
Both will get about an equal mix of winter/summer.
See, my logic is that this morning, after going from 15W-40 to 25W-70, I will have a very clear impression of how it starts and warms up. Then it will run 'till summer.
In summer, I'll grab a sample, and go to the thin stuff, and once again have a very clear impression of how it runs in the hotter months.
Besides, the car is only a 1987 Camira (J Car)station wagon, that I would get virtually nothing for, in spite of it's good mechanical condition (doesn't look pretty).