Americans borrowed more in September to buy cars and attend college, but they charged less to their credit cards for a third straight month. The figures suggest that consumers are growing more cautious about taking on high-interest rate debt in a weak economy.

Total consumer borrowing rose by $7.4 billion in September, the Federal Reserve said yesterday. In August, it had fallen by the most in 16 months.

The September increase reflected a 5.8 percent increase in borrowing in the category that includes car and student loans. But the category that covers credit- card purchases dropped 1 percent after larger declines in July and August.

Credit-card use has sunk nearly 19 percent since September 2008. For many consumers, adding debt with high interest rates is too risky when jobs are scarce.