Once my Inventor hit level 6, the option to detonate things became available... So, I went to the junk yards, dug around, and blew up the heaps/salvage for extra scrap. When I was done there, I went home and found that I could blow up things around my house - including my car. Curious, I saved my game and went to my neighbor's house, who parks their car outside... boom! The 4-Everything van blew up into 4 piles of 42 scrap each. Continuing down the street, I found a Speedster... it blew up into 4 piles of 590 scrap each! Seems like the more expensive cars yield more scrap! Needless to say, "The Scrap Collector" challenge was completed, lol.
-I have not yet checked to see if any relationships were ruined because of the car-bombings (I did it at night when no one saw me, just in case)
-Sims seemed to replace their cars as if nothing happened... bug/glitch? Or do they simply buy new ones?
More testing needed...