If I have a $21000.00 (roughly) car loan initiated in August of 2008, with a rate of 8.1%, can i refinance after a year for a lower rate? In that question, I also would like to know if doing so makes a loan for the entire outstanding balance of the loan, or just the principal. Obviously, it’s pointless to refinance for a lower rate only to prolong the payoff of the same or higher balance.

Assuming there are no pre-payment penalties to roll into the new loan, you re-finance for the principal only.
Unless you re fi the entire balance, you would wind up with 2 payments to pay. Plus if you do re fi, the second loan co would hold title so you have no choice to pay off the balance. If you own or buying a home and have equity in the home, perhaps you can get a second mortgage for 10 years that would greatly reduce your monthly payments. Plus you can always pay extra each month on a 2nd mortgage. You should be able to do it on your current car loan as well without refinancing .