The first test was my oil that stayed in the pan for over a year in a half. I started to lower my oci to see if I can improve my results. Personally I believed that my high iron & silicon is from the long oci of not changing it frequently. My ocd did freak me out for a hot second, and I googled stuff about it.
So I'm collecting all of that iron/silicon stuff from months of holding the oil so long, so I was not too worried. I had Amsoil SS, a reputable synthetic!
Lastly, I only had 4.5qts of amsoil SS in that last oil change, so to fill the rest, I went and dumped 1.5 qts of 5w-30 synthetic castrol edge to get to the full line. All I had. That amsoil guy on youtube said castrol got good reviews by his subscribers and he placed it second to amsoil this or last year for top 3.
Anyways, of course I'm not going to dump amsoil SS after 4000 miles, so I'm now buying whatever is on sale and continue this oci sweetspot. Even though I got a great result, I can't be buying the most expensive stuff to dump at 3785 miles which is appropriate for my severe schedule actually. Hopefully it does the same with the quaker state synthetic I bought on sale that I'm using now without changing my fram ultra until next oil change. Instead of the around $60 for the long Amsoil oci, I'll do about 3 shorter oci of the 15-something dollar quaker state walmart rollback discount while using my filter twice.