<prompt> Human: My credit score is 667 and wont budge, and my average age of credit is what is holding it back, as my oldest line of credit is only 6 months. My dad has a score of like 820 and probably has some super old credit cards. Ive been reading about parents adding their kids as authorized users to a CC. Will this boost my age of credit? Would this lower his score? I wouldnt even want a card or use the account or anything, I just want to boost that average age. Obviously I would talk to him about it, and Im sure he would as long as it doesnt mess his score up. Thanksedit: my payment history is 100 and my utilization is 5 with zero derogatory marks, thats why Im looking towards average age to boost it.edit 2: just pulled my FICO with annualcreditreport.com and yea, my FICO is only 619. It pulls up a lot more older shit that CK doesnt. One of my paid off derogatory marks got erased from CK but is on FICO still, kind of wish I didnt pay it, because I think I might have reset the date for it to fall off. I guess Ill still ask my dad for the AU and keep making on time payments.  <response>: It certainly cant hurt if hes good with his credit. The way to sell it to him is:do not even give me the card, just sign me up as an authorized user, there are zero repercussions for you, dad.Youll get all the benefits from being an AU just by being signed up as an AU for one of his accounts, make sure it is on a card he actively uses. 