Why are present participles used in this way? Do both passage convey the exact same meaning?

Question

Extreme heat also depletes the oil’s additives sooner, altering the oil’s chemistry and preventing it from lubricating, cooling and protecting as designed."

This is the actual writing piece I have found in a blog post. I usually read more like this and the question always had in my mind.

Here is how I want it to be:

Extreme heat also depletes the oil’s additives sooner, alters the oil’s chemistry and prevents it from lubricating, cooling, and protecting as designed.

Why are present participles used in this way? Do both passage convey the exact same meaning?

Answer 1

No, the two versions have different meanings.

The original version can be re-written:

Extreme heat also depletes the oil’s additives sooner, which alters the oil’s chemistry and prevents it from lubricating, cooling and protecting as designed.

Here, "which" refers to the depletion of the oil's additives. So in the original version, "extreme heat" depletes, and the depletion alters and prevents.

In your re-written version, the subject "extreme heat" does three things: depletes, alters, and prevents. This isn't the same thing because extreme heat, on its own, doesn't directly alter or prevent. It's the depletion that does those things.

While it would be natural to attribute the alteration and prevention to the extreme heat since it started a chain of events which caused all three, the original sentence does not have this meaning.