I wish cars ran on pee

Okay I know it sounds gross, but what if cars could run on pee? When the car is running low, you better start drinking a lot of water! And people probably wouldn't use toilets nearly as much, they'd just bottle their pee up till the car needed it. Yes, this is a pretty gross topic.. but seriously! Pee has no purpose, except for those weird nature people who drink it, but that's weird. So I'm just thinking conservatively! Now that I'm really thinking about it, it's seeming like not a very good idea after all.. Just forget I ever wrote this.