99 Alero V6 Gas Mileage issue.

[Blown 346]

I have a 99 Alero that I got for free back in March from my uncle. The car was not takin care of by my cousins.

When i got the car(103,000, now 109,000) I went thru and changed the Fuel filter, air filter, front tires. The gas Mileage Im getting is horrible, I have been mostly driving highway at about 65 70 MPH, and some usual city driving. On a full tank of gas to where I have to fill up Im only getting about 13MPG. Average even city driving I can get about 190 to 200 Miles out of the tank.

I have used sea foam in the gas to try and restore power and clean out the fuel system to help improve my gas mileage. That hasnt helped.

What else can I do to get my gas mileage back. Normally I should be getting about 21 city correct?

Edit... I know the plugs and wires have to be changed, the last time they were done was by me 4 years ago. Would that decrease my MPG by that much.

Any help would be great.

[Nate's Alero]

Here


New Airfilter (Intake...)

New AC Delco Rapidfire plugs

New Taylor Wires

GM top end cleaner

Check and make sure all gaskets are intact, a vacuum leak can kill gas mileage

Using a better oil, can also gain about 1MPG

Quaker State Advanced Protection, i use, and i use a AC Delco PF52 oil filter.

How do you drive as well? hard acceleration? easy going? mixed?

i drive mixed, like going on the highway, i give her a little, but not muhc and not all the time, i get about 24MPG, 99' alero 2 door 3400

i WAS getting about 13MPG, and i did the listed above

[worknprog.99]

due i get around 270 before i start getting worried if i havent driven it hard (gas gauge doesnt read accurate) i think on the highway i get around 31 mpg, something is definately wrong i get around 24 in the city

[Nate's Alero]

due i get around 270 before i start getting worried if i havent driven it hard (gas gauge doesnt read accurate) i think on the highway i get around 31 mpg, something is definately wrong i get around 24 in the city

i dont even get that, i get about 230 before i get nervous, mine reads right til 1/4 of a tank, then goes NUTS

[white04alero]

i get about a constant 230 per tank. and i used to be getting about 200 per tank. all i did was plugs/wires/driving style. driving style helped a lot. i still think i should be getting more than 230 per tank, shouldnt i?

[worknprog.99]

idk lol... i went to cedar point and got 295 miles on it then i filled up and it only took 10 gallons...

[colonel6632]

get an ecotec. last highway trip i averaged 36.6mpg. that was about 1100km

[jackal2000]

the main contributor to gas mileage is the upstream o2 sensor (bank 1, sensor 1). it probably not in the best shape but still not bad enough to throw the malfunction code. i would replace it.

[cherrington17]

upstream 02 (easy to replace w/ the right tools)
air filter
tire pressure

[Blown 346]

I drive nice all the time, unless I have to pass. Then it takes forever for the car to get any power to move.

I will look into the O2 sensor.

[01OldsAleroGt]

see i don't understand it.. the first 6 months i had my ho i was breaking down 320 miles a tank. and im a mixed driver.
Now i barely see 240 before refuelling.

[Blown 346]

Im lucky to see a little over 200 to the tank.


Tire pressure is at 32 all around, air filter was just replaced with a K&N a few months ago.

[99alerogirl]

move outta the midwest man... back in indiana i was lucky to get 200 miles, ever since i moved to utah... i get 270. don't know why, driving style hasn't changed. must be the altitude? i dunno.

[Nate's Alero]

I have plenty of power...., i just dont get good MPG's...

ill replace that upstream, maybe the OP should too

[cherrington17]

well.. its gotta be something...

for OP, is it totally stock, or do you have any work done.

nate, you of all people should know how to keep your car in peak mpg.

[Malibu369258]

move outta the midwest man... back in indiana i was lucky to get 200 miles, ever since i moved to utah... i get 270. don't know why, driving style hasn't changed. must be the altitude? i dunno.

I can vouch for this lol, I lived in Rockford, IL, 2 years ago, and now live in Colorado (5000 ft above sea level) running 85 octane with at least 50 miles more to a tank.

[ServO]

Hmmm I should start looking at my mileage...I fill up every Friday weather I need it or not lol...Usually about 200 miles to the tank...sometimes less, but I occassionally enjoy driving like a 16 year old...especially when theres a car load of 16 year olds next to me at the light.

[clutch1]

Does your temp gauge work? Is it getting to around half way? Does the big coolant radiator hose get hot eventually?

I'd check to make sure the thermostat isn't sticking open, never allowing it to heat up. Also if it appears to be working OK, check coolant temp sensor, make sure it's reading right.

If the car always thinks it's cold, then it'll dump way more fuel in that needed IIRC.

Just another idea.

[Blown 346]

well.. its gotta be something...

for OP, is it totally stock, or do you have any work done.

nate, you of all people should know how to keep your car in peak mpg.

Car is totally stock.

[Blown 346]

Does your temp gauge work? Is it getting to around half way? Does the big coolant radiator hose get hot eventually?

I'd check to make sure the thermostat isn't sticking open, never allowing it to heat up. Also if it appears to be working OK, check coolant temp sensor, make sure it's reading right.

If the car always thinks it's cold, then it'll dump way more fuel in that needed IIRC.

Just another idea.



Temp guage works, but it does start to get warm when you sit for awhile(when its warm out). But then it moves back down to normal op temp. The temp guage sits a little lower than the middle. The upper hose does get hot.

My coolant light comes on, and then goes off when I turn. It seems as if the sensor is bad.

[zzyzzx]

I am also suspicious of your O2 sensor(s). I don't trust them past 100,000 miles.