If the XL1 was equipped with an 18 gallon fuel tank, and you did all highway driving, you could fill it up with an oil change and when the next change was due you could change the oil and keep driving without filling up for and additional 2,400 miles. But it comes with a much smaller fuel tank, because if it could go that long on a single tank chances are the fuel would foul before it got used. The tank is only 2.6 gallons to prevent fuel age related problems from happening. So fill ups are cheap.
Update: Many people have pointed to Snopes debunking this.