The road crews spread an asphault emulsion that 'sticks' together really well. It doesn't soak down into the aquafer anywhere nearly as much as regular oil. I'm sure there is some bleeding of aromatic organics into the soil, but those tend to gas away pretty quick.
I grew up in the day where we saved up oil to paint our carports and foundation peers - the termites wouldnt' touch them. Also, if you saw a yellow-jacket hive someplace, hit it with a quart of used motor oil and it is toast.
Now adays, with a little bit of edumacation under my belt, I see the evil in our old ways. Used motor oil has just about every nasty volatile organic compound in it that you care to know about. It has a half-life long enough to be around when the cock-roaches inherit the earth, and just a little bit of it in our aquafer will destroy millions of gallons of pure water forever.
People like me that rely on our own water source, and my own water purification systems, tend to worry about these things more than the average joe. If my well gets contaminated, I'm in troooooooble.