01 Grand Am SE V6 poor gas mileage suddenly

I am the only owner of this 2001 Grand Am with a mere 28000 miles. It's a great car. However, since I filled up one week ago, I only drove 112 miles and the fuel meter was showing just over 1/4 tank. I filled up and sure enough, it took 9.397 gallons -- that is shockingly under 12 miles to the gallon. Ugh. Last tank, I got over 250 miles and the weather has gotten warmer. Right after I filled up last week, I was having a few starting issues -- it was taking a few turns of the key and Saturday the car lost all power when I turned it off. DH tightened the battery connections and that seemed to fix those problems.

But, what can be causing this dreadful fuel efficiency? There is no loss of power... Any ideas?

Thanks
Laura in NM

Probably nothing wrong, that drastic of a drop in MPG usually does not happen (not saying it cannot, just not normal everyday occurance). The fill-up before the last one may not have been a top-off, also, you may have made a mistake with the mileage and/or the arithmetic. Try it again and make sure you completely fill the tank (sometimes the filler nozzle will act up and not allow proper filling of the tank) also make sure of the mileage. Get back to us next time you figure it an give us the results.

I am the only owner of this 2001 Grand Am with a mere 28000 miles. It's a great car. However, since I filled up one week ago, I only drove 112 miles and the fuel meter was showing just over 1/4 tank. I filled up and sure enough, it took 9.397 gallons -- that is shockingly under 12 miles to the gallon. Ugh. Last tank, I got over 250 miles and the weather has gotten warmer. Right after I filled up last week, I was having a few starting issues -- it was taking a few turns of the key and Saturday the car lost all power when I turned it off. DH tightened the battery connections and that seemed to fix those problems.

But, what can be causing this dreadful fuel efficiency? There is no loss of power... Any ideas?

Thanks
Laura in NM

Maybe a bad O2 sensor??

Probably nothing wrong, that drastic of a drop in MPG usually does not happen (not saying it cannot, just not normal everyday occurance). The fill-up before the last one may not have been a top-off, also, you may have made a mistake with the mileage and/or the arithmetic. Try it again and make sure you completely fill the tank (sometimes the filler nozzle will act up and not allow proper filling of the tank) also make sure of the mileage. Get back to us next time you figure it an give us the results.

I just checked my receipt from the fillup before last. It was just under 10 gallons and I was running low at that time. So, I might have inadvertantly not topped off my tank. I'll know the answer and will post back in a week.

thanks for your help, Jim & Vipey!
Laura

You also could have got some bad gas, or gas that was contaminated with whatever leaks into the fuel tanks at the stations.

I'd try some injector cleaner, Lucas injector cleaner and Seafoam both work realy well as a fuel aditive/cleaner.

With those low miles I wouldnt expect either of the O2's to be bad but could.
And with temprature variations your gas tank can biuld up moisture and this will cause some bad fuel economy.