ガソリンおねがいします! -- Gasorin, onegai shimasu!
二十リッターください! -- Nijuu rittaa kudasai! ("Twenty liters, please!")
The 日本語 (Japanese) is getting along pretty well, I think. Almost done with Pimsleur Level 1. Almost time to stick the set up on EBay and see if I can recover some of my money on it.