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On 6/30/2021 at 6:53 AM, elcamino said:

It’s common to assume that black motor oil has worn out or become too saturated with contaminants to protect your engine and requires changing. Not necessarily. Discoloration is a natural byproduct of heat and soot particles, which are too small to wear out your engine. Since soot particles are less than one micron in size, they typically don’t cause engine wear. For comparison, a human hair is roughly 70 microns in diameter.


If soot particles agglomerate into larger wear-causing contaminants, the oil filter will catch them. Sometimes people who use bypass filtration systems, which can filter contaminants down to two microns, express surprise that the motor oil is still black. Soot, however, can still elude filtration down to two microns. Any finer filtration and the filter could catch dissolved additives in the motor oil.


Years ago when trying out the Amsoil experiment. I say that because we were skeptical of their claims. We used the by-pass from them. No oil change for 50K miles. Oil analysis was fine. Our main goal at the time was our diesel ROW equipment. You go by hours on those, obviously. Amsoil enabled as to double the hours between changes. Time is money. Our biggest savings was hydraulic. Cavitation and contaminants. Again big savings. I started a thread a few days ago about engine loss do to the wrong oil. No takers. Although daily threads about hard part failure. The dogs are at the wrong tree. That’s ok it makes people feel good to change their oil. Kinda like paint protection. 

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I have a 2023 GMC SIERRA SLT with the LZ0 and changed the oil at 2900 miles and had an oil analysis done. The AC DELCO 0w-20 DEXOS D oil was blackish in appearance but the oil analysis showed an oil soot level of 0.1%, a fuel dilution level of 0.4%, and a Total Base Number of 5.45. All of these parameters are well within normal limits. The DEXOS D rated oils have more detergents to keep the soot suspended in the oil as well as having low ash content to protect the DPF. 

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