I have a 2003 Ford Explorer 4.0L and I have noticed it has been getting very poor gas mileage. When I got the car about a year ago, it would get about 325 Miles to a tank. Right now, I am getting about 200 miles to a tank. I have replaced the easy stuff like air filters, and things like that. It runs fine just trying to figure it out. I hate spending $40-$50 on a tank of gas for it to only last like 4 or 5 days, if that. Let me know what you think it could be because I need to get it fixed as I do not make a ton of money. Is it needing a tune up or fuel injectors? Willing to try anything because I can't afford spending this much on gas.