5. There is nothing on our trucks or on a motor stand that would ever need grade 8. Folks say grade 8 because someone else says grade who heard someone else say grade 8. Grade 8 is exrtreme overkill and expensive.
Having had multiple grade 5 bolts fail, I am going to disagree with you here. Grade 8 bolts are a few cents more expensive for 25% more strength.
The added strength and peace of mind is more than worth the trivial cost difference.
The other thing I will add is that you should go to some place like fastenal to get bolts that are *actually* graded rather than just marked. Ace Hardware is particularly bad about selling garbage hardware as grade 8. Pro-tip: if you can twist the head off a 5/8 bolt with a 9" ratchet, your vendor lied about it being grade 8.
