I like your thinking - cheapest synthetic rules! The title of this thread is "Bang for the Buck", now considering that:
Many of us have taken advantage of synthetic oils purported longer change intervals ( I use 20K changes with Mobil 1 0W20)
and have vehicles with nearly 300K miles, motors are quiet, tight, burn no oil, etc.....
These cars are now past 15 years old, and ready for retirement, despite strong motors. How can Amsoil and the high priced alternatives get on the "bang for the buck list" ? Will the dump give me more money if I tell them I used it?
Pennzoil, QS, Mobil 1, Supertech and others simply provide plenty of protection for most applications.