Extension of Oil Change Intervals

Extending oil drains without considering the consequences can cost a lot in engine life. Here we can see two examples of trash trucks where they decided to change the oil every 600 hours of work, regardless of the oil quality.

The first example is a bolivian oil, straight from the drum before use. We can see that the additives do not come close to what they should. It has about 20% of the detergent/dispersant required and 30% of the anti-wear additives. The viscosity does not match what is on the label (15W-40).

New oil

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In the next example we have that same oil after 611 hours of use. The viscosity has increased from oxidation, even though it still has not reached the 15W-40 range.

The detergent started 80% lower than it should, and is now only 3% of what the engine needs.

The anti-wear additives have decrease to 5% of normal.

The TBN (reserve against acids and corrosion) has dropped to less than 0.5. This does not protect anything. This problems passes on to the next oil, as the sludge accumulated in the engine has to be cleaned up by future oil.

Bolivian oil with 611 hours of use
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The next example is with a good North American SAE 15W-40 for the same period of time on the same routes. The calcium (detergent/dispersant) was partially consumed, but remains at 86% of its original value. It also has 15 times more anti-wear protection as the other oil

In reality the oil is not supposed to have to clean up all the mess made by the last oil, but it did eliminate 62 ppm of iron along with the other sludge it took off the walls of the engine.

A good North American oil with 611 hours
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When we compare the used oil from North America with another brand new oil from the drum, we find that even after 611 hours of work it still has 99.3% of the detergent and 95% of the anti-wear additives that the new Bolivian oil has

Another new Bolivian oil
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Here we compare these oils with a new oil from Argentina. It already has 7 ppm of dirt content before putting it in the engine. 10 ppm is considered the upper limit for contamination of used oil.

A new top of the line Argentine oil
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The used North American oil has 11% more detergent and 94% more anti-wear as the new oil from Argentina.

At the time, this was the highest grade oil offered in the Bolivian market by this Argentine brand.
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