This gets bashed...but whatever. The more you pay down your principle, the better throughout the life of the loan. The sooner, the better. You pay interest every month you have the loan out based on outstanding principle. The more paydown, the fastest possible will save you money. I paid down over 100k in my first year ish and probably saved 100k in interest and over 5 years in payments. I like that ROI. Not optimized, but not a bad way to go. I'm back to minimum payments now 2 years in.