You'll probably find a small (1-2oz) jar of "White's Heavy Duty Leather Preservative" in the box with your boots. That's Obenauf's in a different packaging (White's source it from Obenauf's AFAIK). Use it sparingly and that little can will last you a long time. Get a good horsehair brush and use it regularly. Keep the boots clean. Remove sand and mud after each wear with a moist cloth (old t-shirt...), let dry, then use the brush.
8/12/15 at 1:53pm