l got a new *used* 2004 grand am SE1 on friday. It had just overfull tank of gas (since it came from the dealer i'm guess just normal 87). It is two line under a 1/4 tank now and l have 160 miles on this tank. Talked with the service department today (because l have a break noise) and asked them why my gas millage would be so terrible (had a ford taurus wagonon that was a 97 with wayyyyy more miles on it and l got 264 for a tank of gas in that. ) OH by the way this grand am only has 52,000 miles on it. the guys answer to me was. well maybe it is just cause it is a different engine and heavier car. call me crazy but if l figure out what i've used l think it averages down to like 15mpg??? and that should not be normal for the EPA and useaverageses that I've looked up. IT is the usual v-6 3.4L it is a 4 door. Someone had overfilled the coolant resivoir tank before it was ''deliverd'' to me and that caused it to ''release'' coolant (out the the place it is suposed to). And l had weird reving things going on at that same time. It would Idle at 1.5rpm(x1000) but put it in park and it went up to 2.5(x1000) this happend the first night l got it and has not had an idle problem since.

So i'm wondering. Is there something they should be doing to make it get better millage? Do you think it could be related to the engine working hard during coolant release? Just let me know your thoughts please.

could be weak spark plugs causing incomplete burning of gas
also maybe the coolant goes through certain passageways but since if you filled it further it could mix with the air fuel causing for fuel exess consumption.
get a compression test to make sure all cylinders are ok
if you cant try draining the engine by a mechanic and check the transmission also

Very odd, we had a 2003 with auto & the 3.4 liter, it averaged about 27-28 mpg to a tank.
Is there any white smoke coming from the tailpipe? It might have a blown headgasket?
Take it back to the dealer. That MPG is NOT normal, & that car should be lighter & smaller than a taurus. The coolant thing overflowing from overfilling should not affect ur mileage or make the engine work harder, because their is no way for the engine to ''work'' harder on the water pump to push the coolant without changing the viscosity of the coolant, which would be highly doubtful.
There is something wrong with it, go back & complain to who u bought it from.

You bought a ''used'' car, usually they r sold ''as is they do not have to by law fix for free anything if they do not want to. That is why l usually tell people buying used cars to pay for an inspection fee before buying the vehicle. As for the low mileage, take to a good mechanic & have the engine controls & transmission checked. A lot of things can cause low fuel mileage. Keep in mind, u r driving a different make & model, so the mileage isnt going to be the same as ur last vehicle.

first of all, how do u know the fuel guage works? comparing miles driven to fuel guage is never reliable. fill the tank full, drive the vehicle, then refill the tank & divide the miles by the gallons.

If in fact u r getting poor mileage, check for fuel leaks including a fuel pressure regulator leaking into the vacuum line.

l wonder if ur coolant being overfilled was because it was low & they filled it up. This engine is prone to intake manifold leaks which could be external or internal to the engine. As was suggested, pay to take it to ur mechanic or somewhere else than where u bought it & have it inspected.

grand ams do have realy small gas tanks but it might have a blown head gasket

replace spark plugs (make sure they are properly gapped), replace coil and spark plug wires and replace air filter. unless you have already done this this will help make your engine more efficient. My ex girlfriends 4 speed auto was going into overdrive on the highway (youd probably notice this already but this killed her mpg)