I've been messing around with Excel to see the actual difference, but I had to make some assumptions. Assuming your minimum payments are $300 and the total you can use towards debt is $1500:
- If you pay $300/month towards Big Loan and $1200/month towards Car Loan. The car would be paid off in four months, then after four months, applying a full $1500/month towards Big Loan it will be paid off in 14 months. Total payments of 19521 or $955 in interest.
- If you pay $1200/month towards Big Loan and $300/month towards Car Loan. The car would be paid off in sixteen months and the Big Loan it will be paid off in 13 months. Total payments of 19398 or $832 in interest.
Difference of $120. If you want me to plug in some different numbers let me know.