Archived from groups: alt.games.grand-theft-auto (More info?
If it's with a cheat code, then you will get the warning every time you
save your game. This is partly to warn you that you might experience
glitches, such as all cars being white forever, and partly to tell
anyone using the game save that it was achieved using cheat codes.
In my experience, the only car spawning that crashes the game is with
the garage edit mod for the PC version. This sometimes crashes the game
when you go to the garage after spawning a car in it.
If you just want to have a go in the cars, spawn them and don't save.
If you want to put one in a garage, why bother? You'll just have to
spawn a replacement when you roll it, so why not spawn one when you