Link to YouTube to see how to convert your Preppy.
Platinum Preppy pens are pretty well known in the pen world as being one of the best values around, with a list price of only $4. It's sturdy, reliable, attractive, and works well. For the true ink addict, they are indispensable.
The bodies of these pens are perfectly suited for an eyedropper conversion, which means instead of getting a $7 Platinum converter to use your bottled ink, you can use an o-ring and a little silicone grease and you can fill the whole body of the pen with ink. Not only do you save cash, but you also increase your ink capacity by about a bajillion percent.
The conversion is simple, I would guess it'll take you about 20 seconds. The only thing I want to point out is that with any pen that has this large of an ink reservoir, you might want to keep it at least half-full at all times. You *may* experience some ink 'burping' (air bubbles coming out of the nib) if you get below half full. Why? This is up for debate, but I've heard the heat from your hand raises the temperature of the air inside the pen body, and the difference in pressure causes it to come out of the only place it can: the nib. Is that true? I'm not sure. Just use the pen as long as you want, and if you notice it burp and you see you're low on ink, fill it back up!
And the silicone grease?