Depends on the compound rate as to how much you could "save", however, most likely - wouldnt help at all.
What would help, is to pay extra per month, that way the principal is paid lower, thus, less interest can be added due to the reduced principal.
For example:
lets say you owe 10K
10K x .16(your % APR) = $1600 / 12 months = average of $133 in interest per month
if you pay 450, only about 320 is going towards principal. If you were to pay, say, 550 per month, 420 would be going to your principal, reducing your principal about 1200 per year, which is less they can charge you interest on.
That all being said, the compound rate is most likely every month (ive never seen anything but that on a car loan). On the bill, you should see a "Periodic Rate" which is the rate at which they are compounding your interest every month. Should work out to be your APR or darn close, however, by compounding monthly, and you paying the minimum, you are never going to end up paying less, or saving money. The only way to do that is to reduce the principal by paying more than the monthly payment.
If your scores and reports have gotten better since you opened the loan, however, you might consider refinancing with a local or national credit union. They will most certainly give you a much better rate than 16%. Even with your scores listed below, you should be able to obtain a much much better rate at a CU. I think Navy FCU's highest rate is 12%, which at worst, would still save you over $400 a year in interest if you refinanced at 12% assuming 10k balance.
