What's the difference between a gas tank and a gas chamber? You don't fill a gas tank with Jews!
Why would you draw a comparison between gassing Jewish people and filling up a gas tank? I think that's really anti-Semitic.
Because that's what the gas chambers were used for. Also you don't put any Jews in a tank, it should be a specifically factory designed to kill them.
Jokes about the Holocaust and how Jewish people were killed in gas chambers is something that a lot of people would consider offensive to hear and therefore it's not something appropriate to joke about. Since so many Jewish people died during WWII, the effects and pain of that are still felt by Jewish families today. I think it would beneficial for you to visit the Holocaust Memorial Museum, online or in person, and gain an understanding on why we shouldn't trivialize what happened in WWII.