I have no GF, not because of my supra mainly because girls in MO are nuts and wierd and when I find one that isnt shes married or involved so yea its shitty here, LOL.
I do think if a girl is jealous of an inanimate object, such as a car, then she is so insecure with herself that she wil probably eventually cheat on you, or at the very least come close because they are looking for that attraction from someone, anyone, and they think you're not as interested in them because you actually take time to work on your car etc.
Food for thought, I could be wrong but that situation is highly unlikely........LOL