Oil Change?

[KawaiiKoneko]

I have a friend who wants to come and see me. But the trip here and back would require him going 500 miles over the recommended (assuming it's 3000) miles before a change. Not only that but he hasn't had it changed since January-Decemberish. It's a 2003 KIA RIO and he hardly ever drives it. When he does it's normally not in the day time unless it's a necessary trip. I've been trying to figure it out since 10am this morning but can't find any good sources that don't seem to have a liberal agenda or greedy companies wanting their money.

Why is it so important to change the oil often? What happens if you don't?

I'd really appreciate some sources as well. I'm skeptical to any claims about it. And I'm sure you'd be too if you've been reading nothing but empty answers all morning. u.u'

So if someone could help me out and try and explain the process of it all (why changing is necessary, what happens if it isn't, what process do the chemicals go through when left in certain temperatures and how it effects it, etc,) I'd really appreciate it.


Thanks <3