2002 Saturn SL2 MPG is way off

First of all thank you so much for your donation. Iam not saying you don't know how to figure out gas mileage but I have to ask you how you figured out you got 20 mpg. As many year's as I have worked for saturn dealer's that is the first question I always the customer when they come in for low gas mileage concern. Because out of all the customer's that came in with that concern most just didn't know how to figure out gas mileage.I just don't want you looking for a problem that's not there. As far as your power loss goes is that all the time?Or only when hot or some other time?Do you have any trouble code's?If you haven't checked for code's please check now and bring me back the code number's if you have any?

You didn't mention all the step's you took for figuring out gas mileage. You reset the trip odometer fill the tank till the pump shuts off and your tank is full. Then drive the car and when you get gas next time fill the tank again till it's full and the pump shut's off. Then take the number of mile's driven on the odometer and divide that by the number of gallon's of gas it took to fill the tank back up.I haven't really used or heard any feed back on how the Lucas fuel treament work's.I have used alot of the Lucas oil stablizer though and I like that. At Saturn we used chevron techron fuel system cleaner as per Saturn to clean the dirty injectors under warranty repair's.I know that stuff work's well. Another thing that help's to keep your car running smooth is putting in a good quality fuel dryer in your gas tank every so often. You can get water from gas station's when you least expect it. That's strange that you have lack of power at high way speed's and plenty of power excellerating from a stop. Low fuel pressure clogged cat restricted fuel filter stuff like that cause's lack of power. If that mileage is correct your filter should be good they get changed every 100,000 mile's but I have seen the fuel pressure regulator in them fail early and cause problem's. You would have to perform a fuel pressure test to see if that went out. You said it's getting better as far as power goes though so I would give it a little time and see if it get's better. As far as your low fuel mileage I would never be concern based on one low gas mileage on any tank of gas.I would give it atleast three tank's to see how it change's.