The conventional oils available in the 1970's were good enough to enable Toyota engines to run over 500,000 miles:
1974 Toyota with 482,000 miles:
http://i5.photobucket.com/albums/y18...tech/18rcb.jpg
1977 Toyota with 600,000 miles:
http://i5.photobucket.com/albums/y18...leowrfield.jpg
The 1977 Toyota owners manual says: "Use 20-40 or 20-50 weight if normal temperatures are above 10 degrees F." In other words, even extra thick 20-40 and 20-50 CONVENTIONAL oils provide sufficient protection to prevent significant start up wear at temperatures above 10 degrees F. And since todays conventional oils are thin 5W-20 oils, start up wear is even less of a
potential issue, especially in mild winter climates like Los Angeles where you live.
The "better flow properties" of synthetics are marginal. Example: A 5W-20 conventional oil at zero degrees F will actually flow slightly faster than a 10W-30 full synthetic. This is easily demonstrated by putting samples of each in your home freezer.
In the end, owners in mild climates who use synthetics are choosing them for emotional reasons. None of these synthetic using owners can provide even one case history example of a Toyota engine operated in a mild climate that suffered heavy piston ring, bearing or camshaft wear, loss of compression, sludge, etc. when lubed by a conventional oil that was changed every 3-6 months or 3000-5000 miles.
However, there have been a few Toyota engines (e.g. the 22R series engines) that suffered timing chain mechanism wear before the 500,000 mile mark even if the owner changed the oil every 3000 miles. But in those cases, the owners who used synthetics had the same wear problem at the same odometer mileage as the owners who used conventional oils.