How can I save lighter fluid in my Zippo lighter?

Sounds like you need to replace the cotton wadding inside the lighter. I had this problem after I wash pushed into a pool with it in my pocket and it got flooded out. I had to replace everything in it, wick, flint and wadding.

Buy a recommended wadding from a tobbaconist, the cheap stuff from the supermarket doesn't work very well at all. If you buy the Zippo brand wadding the bag should have instructions on how to pack it with the wick intermingled amongst it. There's a fine line between over packing it which means it won't absorb as much fluid as it should because the wadding has less room to expand which will increase your refill rate and not packing enough wadding which means you won't have enough wadding to absorb a good amount of fluid and you're stuck with the same problem. Once you get it right though it should be like new