Improving fuel mileage on my Grand AM

I just recently purchased a 2003 Pontiac Grand AM, V6. I took it to my mechanic for a tune up ( spark plug, fuel injection cleaning, wires and oil change) after my father and I both noticed the gas gauge moving toward empty quite a bit after just a little bit of driving. My mechanic said that the diagnostic was showing the car was firing properly and that these models generally don’t get good milege in the city. I am close to using three quarter of a tank and have only traveled 200 miles. What could be going on with my fuel efficiency?

Maybe the gauge is wrong. Only way to tell is over the course of several tanks full of gas, divide miles driven by gallons used.

My Dad has this car and is also disappointed with the mileage. Anything over 25mpg highway and you are doing great.

You can’t tell anything for sure about fuel economy by using a gas gauge.

Fill up the car and set your trip odometer to zero miles - or write down the car’s mileage.

Drive as normal for a while until you’ve filled up the car again about 5 times. Each time you fill the car keep a receipt or write down the actual number of gallons it took to fill the car. When filling the car just go until the automatic shutoff kills the pump. If you want to really go crazy use the same gas station and gas pump.

At the last fill-up add up all of the gallons. Now divide the miles driven by the number of gallons.

Then report you actual mileage and we might have something to talk about.

As others have said, we need the real miles per gallon number before doing too much work here.

However, have you made sure your tires are inflated properly? Underinflated tires can kill your mileage (and possibly you).

How much city driving and highway driving do you do? Do you drive gently or aggressively? Do you carry a lot of passengers and cargo?

@chale, maybe you have unrealistic expectations. My Honda Civic gets 29/36 MPG (city/highway), and holds 11 gallons. At 30 MPG, 3/4 of a tank takes me about 225 miles, so if your powerful V6 Grand Am takes you 200 miles on 3/4 of a tank, there’s probably nothing wrong.

Thinking of the last time I rented a Grand Am, I remember that it was a pretty powerful car, and when you have that kind of power, you’re going to use it. It’s hard to drive a car like that and get decent fuel economy out of it.

Basically, if you wanted good fuel economy, you bought the wrong car. You should have gotten something with less weight and a smaller, less powerful engine.

Considering the car was just in the shop, the tire pressure is probably fine, and the only thing to change is the driver’s habits. If you can bring yourself to drive this car like an old lady would, you may be able to improve your fuel economy.

Change the thermostat.

You have been given good advice. Check your mileage by filling the tank and noting the odometer reading. When your gas gauge gets low, fill the tank again and note the odometer reading. Subtract the first reading from the new reading to get the distance you traveled. Divide the number of gallons you pumped into the tank when you refilled the tank into the distance traveled. This will be your miles per gallon.
You can do a quick check on the engine thermostat by noting whether or not you are getting warm air from the heater. If it is cold or tepid, the thermostat is probably the problem. Another check is to look at the termperature gauge and make sure it comes up as the car warms up. Buy a tire gauge and check the tires.
Gas gauges are a poor way of measuring mileage. I have had cars where the gauge stays on the full mark for quite a while and then drops rapidly. I have had cars where the gauge drops rather quickly and then hangs around 1/4 of a tank for a long time. My 2011 Toyota Sienna gas gauge drops to below 1/2 tank rather quickly. However, on a 375 trip this past Saturday, our average was 26.2 mpg.
If your car is running well and the tire pressures are correct and the thermostat is functioning, you car is o.k.

Gas gauges are useless for measuring actual mileage. This is often do to the irregular shape of the tank. Take treidag’s advice and do it scientifically. Get back to us if the trip mileage is really low.

just wanna point out that the fuel injection cleaning you paid for was comepletely useless, and could have probably bought a couple tanks of fuel for you