Pump related question

Hello Guys,

Can I use Vaseline as a lubricant for pumping ??

Does it have any side effects or is it safe to use ??

One more doubt - Actually I'm a beginner for Pumping, right now I'm using an electric pump 17-21 kpa. I see a great expansion in size like 2-2.5 cm more in length compared to my Erect Length while pumping.

Well does that mean that's the possible length size I could get by PE ??