I am on my 3rd vehicle using synthetic oil. I DO NOT CHANGE MY SYNTHETIC OIL. BUT I CHANGE THE OIL FILTER RELIGIOUSLY EVERY 1,500 MILES. My source of this decision, one of the major oil corps.This is off subject but I know guys that work at/for TRD and they swear by Castrol GTX. They have told me that they have seen multiple failures using synthetic but never a failure using dino oil. I am using GTX in my cars and dirtbikes from now on. Can't beat the price!
They had tested this procedure over a long period.
Between my 3 vehicles there is a total of 600,000 miles. I started this program in 1991. Vehicles were and are; 1988 Cadillac Seville, 1988 Toyota extra cab four-wheel-drive 4 Cylinder engine cylinder engine and present a 2005 Toyota Tacoma 4 L 4x4.
I was informed that the synthetic doesn’t wear out only becomes dirty and the frequency of the oil filter change corrects the dirty problem.
Of course when you change the filter there is loss of oil thus need to add some and over a given time you have changed the oil a few times.
I also take an oil sample to CAT for Analysis and based on the result test sheet my oil has been good.
You might ask why didn’t they share it with the public. It is a very easy answer...