From the perspective of credit mix alone, a perfect 850 has been achieved by many people having one open loan and a few open credit cards. The loan can be of any type: mortgage, student, auto, personal.
It is possible that some FICO models might give you a few extra points for having certain sub-categories of accounts. Examples:
Revolving:
* Instead of credit cards alone, you might get some extra points for have both credit cards and a charge card.
Installment:
* You might get some extra points for having multiple sub-types of installment accounts, such as mortgage, student, auto, and personal.
The above "extra points" are all highly speculative, and nobody has shown conclusively that you get any extra. Because it is speculation, and because some of these are costly, nobody should ever add an account chiefly out of a desire to chase this "benefit", which may be a phantom anyway.
Two caveats:
* If a person has no installment accounts of any kind, adding a loan probably makes sense. In this case use the Share Secured Loan Technique.
* It is known with high confidence that the Auto Enhanced flavors of FICO do like it when you have an auto account on your profile. It's not clear whether this needs to be an open account. Regardless, no one should add an auto loan to chase this benefit.
