Look up some missions done by PLAD to see just how much you can save if you really know how to exploit gravity slings. He even made a tool that lets you calculate gravity assists. LKO -> Jool for 1051 m/s and 1011 m/s Kerbal-X to Duna surface and back I am not really all that good at gravity assists, but following his example I was able to get from LKO to Jool for ~1250 m/s, which was one of the most satisfying experiences I ever had in KSP.