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Balances on installment loans such as mortgages have only minimal impact on your FICO score. Paying down your principal balance may not have any discernible effect on your score.
This is a regular mortgage, not a HELOC, correct?
HELOC is a home equity line of credit, which is sometimes treated as revolving debt and is scored like credit card debt.
Your auto loan is also an installment loan, so like the mortgage the balance is not going to have a tremendous impact on your scores.
If you have any credit card debt, that is where you should be focusing your efforts.