Let me tell you again. People here say, well, it costs too much to test your oil, it’s cheaper to just change it.
The oil tests don’t just test the oil for remaining life. If that is all they did, yes, it’s cheaper to simply replace it.
They check for various contamination things. Essentially, it tells you if any part of the motor has a problem. Valve train wear produces certain contaminants. Ring wear, different contaminants. Blow by, they can and will tell you. Antifreeze internal leak, they tell you.
Once you fully understand the results, you also understand it’s like having a microscopic mechanic wandering around your motor looking at everything.
And, also the amount of additives remaining in your oil.
If you do this once for each drive cycle, that is, how you drive the car, summer long trips or short trips; winter short trips, you can then estimate how often to change the oil during that drive cycle. So, you do not need to do an oil test every time you change oil.
Several years ago, I got tired of the constant guessing how often to change oil, and had the oil tested in my 2002 Sienna at around 8000 miles, I forget now. I learned that not only was my motor in great shape, but the additives would be good for at least 11,000 miles.
I was at the time driving 25,000 miles a year, almost all long distance highway driving, outside the Snow zone, and using Mobil-1 EP. After that, I changed the oil at around 7000 miles.
If I had moved back into the snow zone, or changed my drive cycle, I would have tested it again.
From time to time a poster will pontificate, if you really care about your car you will do what I do…
Actually, if you really care about your car, you will either change the oil more often than recommended, OR will get the oil tested and find out what is really happening. No more guessing.