on my 2000 mc ss my gas gauge be every where , it dont read right, some times it be full and empty, how can i fix this problem please

 

I have heard that it is a common problem in the 5th gen montes, i have the same problem with my monte not sure if it is a way to fix it but dont quote me!

 

it could be your sending unit has a bad ground due to rust / normal wear, but more than likely its the sending unit itself, which lives in the fuel tank. its a pretty expencive part, personally i fill the car depending on the tripometer, IDK how far you would wanna go with the 3.8 but my '97 LS with its 3.1 i usuallly go around 200 miles before i fill it up, its got a 16 gallon tank and will usually take 10-12 gallons at around 200 miles. due to its differant size, the 3.8 is gonna get differant milage, so you probibly dont wanna follow my numbers, lol.

good luck getting everything sorted out