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Oil condition from appearance?

Personally, I see nothing wrong with picking a number on the conservative side and going for it.s I do consider it guessing, but with modern oil guessing is usually plenty good. Better to do better than to do worse.

However, in my case, I view that as guessing. If you want to stop guessing, in each cycle (winter/summer/etc) have a lab test when you change it, and find out just how good that oil still was.

After years of this constant guessing, I had my Sienna tested with 8500 miles of non-snow zone highway driving, tested, and found that oil was still in good shape, could have gone well over 10,000 miles. So, until I had to park it in the USA, under the same conditions as tested, I changed it at around 7500 miles.

A different car, such as the Mexican 2009 Sienna I have now, I will tend to change it more often until and unless I get a chance to test its oil as well.

When you say extending the life of the oil that implies the oil is worn out or nearly so. IF you test it, you may find it is not worn out at all. Of course, you may also find out it is more worn out than you thought. Depending on your use and the car itself.

There is another reason to test it, and the condition of the oil is trivial by comparison. The test tells you great details about the condition of the motor. The bearings. The valves. Blow-by if any. Head gasket condition. If anything goes wrong in your motor the oil test will tell you, but only if you have your oil tested.

I use Blackstone, because it’s the only oil lab I have heard of. If it’s a good lab, which one you use probably doesn’t matter.

What I mean by that is extending the time you use the oil before changing it. The oil’s actual usable “life” is a different question.

I have nothing against testing, but to me it seems simpler to just go ahead and change it if you’re concerned, as I am. Environmental conditions where I live change frequently (New England has a famous saying “if you don’t like the weather just wait a minute”) and the stresses on an engine can vary dramatically with the weather. It can be 20F and a blizzard on Monday and 65F and sunny on Thursday. It happens frequently. And in winter it could be below 0F for extended periods in the winter. To me, where I live, using oil analysis to create a change regimen would require frequent testing and analysis of the results correlated with weather, driving environment (did I go to Boston a lot or just local?), and perhaps other variables than is practical. Warming up the car in the morning when it’s subfreezing is a major variable, and my old bones no longer tolerate the freezing temperatures as well as they once did.

In summary, I’m not against testing to determine frequency for those willing to do the analytical regimen, but in my case it just doesn’t seem a practical solution. I suspect my case is not unusual.