Talk:Engineering Lab/@comment-199.241.203.29-20130510185336/@comment-4557698-20130510195907

It depends. From my personal experience, I'd say 1 in 40 at most. That is, after 40 times you should have upgraded it. Then again, it's a random chance, in the same way that you can sometimes upgrade a part from L1 to L4 without breaking it once, but you can also fail the L1->L2 upgrade.