Helping sister improve score for Auto loan

[FroggieMom]

Hi All!  I have a quick question for the credit gurus out there.  My sister is in need of a new(used) car.  She successfully paid her current car off in Sept, and that is her only auto loan history.  She has no major credit cards and only 3 small store cards with limits of $500 or less each, so a very thin file.  Her FAKO CK scores are in the 640's.  Her last car loan was with Cap1 at the ridiculous rate of 15%! My question is this -- I'm willing to add her as an AU to one of my older MC if boosting her score that way would help her secure a lower interest rate, will that help?  

[jeffm4688]

With previous auto loan history it shouldn't be terrible to finance another car at a much better rate. 

Fako scores aren't useful, especially in auto lending. In my case my FAKO's are in the 640 as well but my TU auto score was 699 and I got approved for 3.3% through a credit union without issue. I'd suggest she pull her actual auto scores and see where she stands, or maybe consider stepping into a credit union and attempting a pre-approval for the amount she would need.

[Anonymous]

Cap 1 has a auto preapproval site that doesn't do a hard pull.  She can try there to see what rate she can get.  It will give a range depending on the age and mileage of the car but she will have a ballpark.