2001 Oldsmobile Alero Bad Gas Mileage

Since it smells like gas, you should check to make sure there are no leaks in the gas tank or fuel lines or anywhere else gas can leak. You may think it's not leaking because there's never a puddle of gas under your car, but gas evaporates very quickly. Also, this probably isn't the main reason, but if you haven't changed the air filter for a while, you ought to because dirty air filters reduce gas mileage. (Up to 20% I've read)

I have not smelled gas since changing the Fuel Pressure regulator it just seems this car is using an excessive amount of gas like I said about 95 miles on a half tank I have read some articles that say this car gets between 17 and 20 MPG yet it's counter part the Pontiac Grandam gets between 23 and 25 that doesn't sound right to me. There must be something I am missing as I said I am thinking about changing the O2 sensor but I don't have any Check engine light that is comming on so I am not sure if that is the problem. The car runs great plenty of power and doesn't miss, hesitate, or sputter or anything out of the ordinary. The gas mileage is the only complaint I have about this car.

I bet you're right that it's the O2 sensor. Since the check engine light isn't coming on, it could just be that the sensor is dirty but other than that nothing is wrong with it. If it's covered in dirt or grease etc, then it's probably not getting the right reading of oxygen and therefore sending more (unneeded) gas to the engine. So if it's the O2 sensor, you should probably get it replaced, but if you're short on money or something, I bet you could just get it cleaned and then it would work right again. (I'm not sure though). Also, about the gas mileage between your car and the Grand Am, I looked it up and the original fuel estimates according to fueleconomy. Gov are the same for a 2001 Alero and a 2001 Grand Am, 21mpg city and 32mpg highway. The "new, more realistic" estimates are the same too (19mpg city 29mpg highway). Also one more tip to get better gas mileage once you fix whatever is wrong right now is to use synthetic oil. I've read that it can increase mpg by about 2 or 3 compared to conventional oil and it also lasts longer. (I haven't tested it myself yet though since my old non synthetic oil doesn't need to be changed yet in my car)