Question about my interest rate for a car I bought.?

Alright, well I bought my first car on Sunday. I'm in the Marines, and purchased a Subaru WRX for $9,900. However since my credit score is 0. Navy fed could only get me a loan at 15% interest. My monthly payment is $240 a month. I deploy to Afghanistan next month and will be able to make $1,000-2,000 monthly payments while I'm over there. Basically my question is, if I make larger monthy payments will I be paying less on interest?