Actually (ROTF!) my truck came with it's own dashboard saint and I've left him/her where s/he is! I don't like to tempt Fate!
Well, you know that dashboard saint only work if your vehicle is Catholic; sometimes evangelical, but definitely NOT Jewish. You want REAL mechanical problems? Plant your St. Christopher on the dash of a Kosher Chevy.
Also, even if you've got a proper Catholic vehicle with a properly installed dashboard saint, you still have to freshen 'em up, once in awhile. Can't let the thing get all cracked and yellowed in the sun; it ain't respectful and will surely lead to problems.