Why does saliva clean so well? I notice that saliva seems to clean well, much better than plain water. For example, tar spots on the car can be difficult to get off. I typically use really powerful solvents to get them off, like 95% acetone and things like that. Yet, saliva works too. 

Why is this?
Saliva has alpha-amylase (ptyalin), which hydrolyzes carbohydrates (so starch starts to taste sweet in just a few seconds), kallikrein, an enzyme that breaks down protein, and lingual lipase, which helps disintegrates fats (lipids).

So next time you clean off a splattered insect from your wind-screen (windshield, should you prefer), think of it as external digestion, as practiced by flies and by starfish. Or perhaps you might not want to consider that thought...