Jerry
While your analysis on start up wear all makes sense, I have seen bearings, both main and rod, that have come out of well maintained engines that have been run many, many miles and therefore have had hundreds and hundreds (if not thousands) of cold starts on them. If the
oil and filter have been changed regularly and replaced with good quality items and the engine has not been abused, those bearings look almost new, so start up wear on bearings cannot be too bad.
Do you ever rent cars? I do, often, at airports where the car jockeys drive me nuts. In the middle of the winter, they will fire up a cold engine, pop it in drive, and hammer the gas to the floor. Now we are talking about severe start up wear. I decided many years ago that I would never buy a used daily rental car.
I have a question for you. I have a new Explorer with a 4.6 L V-8. Ford recommends 5W20, year round. It just doesn't seem right to be running in the hot weather with it so I used Castol GTX 5W30 this summer but I will switch back to the 5W20 for the winter. Why would Ford recommend such a thin
oil? Does it have to do with gas mileage?
By the way I run Castrol GTX 10W30 or 15W40 in my Cobra. The higher viscosity 15W40 gives me better hot
oil pressure at lower revs in the hot weather. Both give about 55 to 60 lbs cold and 50+ lbs hot at highway speeds. Maximum oil temp that I have observed was 230 degrees, the engine temp was 195 or so at the time. Great thread, interesting stuff.
Wayne