I carried out another small experiment that I thought might be interesting.
One photo shows three fresh oils straight from their original containers:
- Total Quartz INEO ECS 5W-30
- Total Quartz 9000 Energy 5W-40
- Total Quartz 9000 5W-40
As expected, all three have the normal light amber color.
The other photo shows the same three fresh oils after I added exactly
20 drops of the used oil from my TU5JP (NFU) engine to each sample. Even with such a small amount, all three oils turned a very similar reddish-brown color.
This suggests that the fresh oil itself is not responsible for the color. Instead, the used oil contains something with a very strong coloring effect that immediately changes the color of any fresh oil it mixes with.
The question is
what exactly causes this. Is it simply a normal chemical change in the oil's additive package (antioxidants, detergents/dispersants), dissolved engine varnish, oxidation products, or something else?
I have contacted an oil analysis specialist recommended by TotalEnergies and sent him all the details together with these photos. As soon as I receive his professional opinion, I'll post it here.
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