My 2007 mercedes benz c230 was purchased 4wks ago. I have gone through several tanks of premium gas. I have always ran it past the 'low fuel indicator" level glowing yellow, and only get about 300 miles per tank. I can only squeeze in 13.7 gallons every time! The book and web, states it has a 16 gal tank. Does this mean theres still 2+ gal in there even though the lights been on for 30miles? Any thoughts?