I never paid attention to my 97 2.8's MPG until the last couple of months of so. I don't have a OBC. What I got is about 20 MPG, but when I hit about 250 miles on the trip meter, the gas gauge on the instrument panel goes to very low. I am wondering how much miles I really have after that point. If I filled up the gas tank at that point, it only fills in about 12 or 13 gallons or so.