With my 2003 EXV6 Sedan, I am seeing very low MPG. I am at ~ 2800 mi. on the odometer. My terrain is hilly, I ascend up and down a hill everyday between work and home, not to mention stop and go traffic. What I am seeing it that every 180-200 miles my low gas indicator light comes on and I have to fill it up. I use regular unleaded (87 octane). Is there something wrong with my car, or is it because of the hills?