I have a 1999 Mercury Grand Marquis that I have just purchased?

[nickolodeon]

I had the same car only my old was is a 1997. My 1997 gets on the road 28 mpg probly 22 in town and around but this other one I have purchased is getting poor gas mileage, like 13 or 14 in town and around. Well I can fill it up and set my mileage deal and when it hit 200 miles I am totally empty...on my other one I get 300 miles or a litle more. Could their be a cmputer chip out causing this, where do I begin to find my problem and I know I will eventally have to take it to a mechanic but I thought some mechanic could give me some suggestions, before I spend a great deal of money. We love these cars, but I have to have better gas mileage than this.

[miked452001]

I don't know how your 97 could have been getting that high of mileage that is more then i have ever known one to get. Every car is not the same by any means you could find another 97 and it wouldn't be the same. Certain changes from year to year effects gas mileage so my guess is there is nothing wrong its just that there is something different about the 99 models. But I would find another way to check my mileage what you are using does not seem reliable way to calculate.