Pontiac Repair: burning up gas quick, chevron techron, fuel milage

Question
I've noticed that my basic 2005 grand prix 3.8 scfi engine is not giving me the mpg is suppose to give me. And when I bought it the gas guage is bad by over a quarter of the tank I don't if that's wats causing the problem.thanks for any advice.ps I get like 240mpg when its suppose to give u 300mpg(88500miles)  

Answer
Hey Jose:

Well first off if the Gas gauge is erraruc under 1/2 a tank chnace s are the level sensor in the gast tank is going bad. VERY common. usually over 1/2 tank theyare okay under they start to get erratic. As far as MPG if your getting 24 MPG that is not bad. It depends on a lot of factors driving habits are first and foremost. A heavy foot = low MPG. secondly is climate you live in if it's a cold cliamte the MPG are going to be less.If you do mostly city dribing the milage will be less. The type of gas you put in it will effect it as well if you use 87 octane fuel you will get the best fuel milage. higher octane fuel will give you less milage. lastly basic tune up parts at 88,000 miles it's pretty much due for a tune up. spark plugs only AC delco plugs and spark plug wires. A pcv valve only AC delco as well and a new air filer. You may want to try a few bottles of a product called Chevron Techron in the gas tank that will do a great job of cleaning the fuel injectors. Good luck :)