Oh, wow. I apologize. I can be more passionate than necessary at times. I realized afterward that you were referring to my 20K oil and not the 7.5K Mazda recommendation. This microGreen thing is an experiment for me. I do think oil is important, but I think it tends to get blown out of proportion, possibly because there are fewer things people can, or will, do on their cars now. My last vehicle had 350K miles on it when I had an accident in it. My daughter's car has 220K miles. So, I have never observed any ill effects from 10K oil changes (with synthetic). I figure even if my UOA doesn't come out that well I'm not going to wreck the engine with this one extended OCI. I got over switching from 3K to 10K back in the 80's.