Those Amsoil brain washed followers are the victims of of some sort of religious propaganda
John1: Why would you switch to synthetics?
If it is to feels better? go ahead, do it. Do not expect more mileage, more mpg, a longer engine life or reduced maintenance. Do not expect better performance,Extended oil change intervals are probably the worst thing you can do to an engine.
The same amount of acid, soot, fuel deposits, metal shavings, silica, dust, rust, and about 10 other contaminants will accumulate at the same in your engine whatever the type of oil you will be using.
I just sold an old 260E with 468K on the clock and all tis car has drank since day 1 has been regular dino oil, replaced at the prescribed intervals.
But if you feel better with synthetic, make yourself a favor, go fo it.