Here is my recent oil analysis on my Mazda CX-9. My 5 years of dealer Castrol GTX 5w-20 every 6 months has ended and this is my first synthetic run at 9 months, 4,780 miles. I ran Archoil 9100 this time and the analyst didnít see my notes, thus they indicated coolant leak. I wrote Blackstone Universal Averages next to metals for comparison. Good to know I can go a year or more if I want. Ran Pennzoil Ultra Platinum 5w-20 without any additives this OCI.