2004 2wd aztek bad gas mileage

I have 2004 2wd aztek. About 3-4 months ago I changed the pcv valve, fuel filter, air filter, and cleaned the throttle body and mass air flow sensor. I haven't changed the plugs and wires yet. Its been about 2 years since changing the plugs and wires. I always fill the tank up because it used to last longer. After changing all the stuff I listed above, the gas mileage went from about 300 miles a tank, to almost 450 miles a tank. Since then it has dropped back down to the 300 miles a tank. Would plugs and wires really cause the big of a drastic drop in mileage? Is there anything else to check, clean, or replace? Thanks to everyone.

That is a huge drop, roughly 33%....

But you are basing that on a gas gage that could be erratic.....

Best way, is to fill the tank.....set the trip odometer to zero......never let tank get below 1/4(keeps the fuel pump cool,).....fill her up again....write down the gallons put in.....do this for about 3-4 fillups to get a better reading.......then just add up the gallons, and divide them into the trip reading to get gas mileage( I do it this way, even though I have a cluster that does it for me.....)...

Reset the trip, and do it all over again to monitor your gas mileage....

Original EPA mileage was 24/17, or 20 combined....

Not really the answer I was looking for, but I do appreciate it. Thank you

Not really the answer I was looking for, but I do appreciate it. Thank you



It might not be the answer you want, but it's the right answer. :wink:


Its quite possible that after not servicing those parts for 2-3 years the millage would improve when you did.
It is however not very likely that the millage would suddenly drop off again after only a couple of months, because of those parts.



With out a proper measure of the millage you've been getting it is impossible to tell what the cause for the change was, or, and this is the important bit, if there was even a change to begin with.

Ok, at last fill up it took around 16.5 gallons. The fuel gauge is on quarter of a tank right now, and I have drove 250 miles. 250 divided by 16.5= 15.15. I should be getting better than that. Any ideas? Thanks everyone.

You need to fill it up again, and use that fuel amount to do the calculation.

The fuel gauge is not accurate enough.

I don't understand why I need to fill up again and use that fuel amount. You mean use the amount of fuel it takes to fill it up from a quarter tank? Then what drive to a quarter tank or until light comes on? I don't care about the right amount, just want to know how to fix it. I need ideas on what could be causing this, not how to calculate the right mileage. I know regardless its getting bad gas mileage. I need to know how to fix that. Not how to calculate the mileage right. I understand it could be a few things but you telling me how to calculate it right isn't really helping me, sorry. I have always used this sight to figure out problems and will continue to do so. Any help on identifying the problem would be helpful, not on calculating the mileage. Thanks

Until you can correctly calculate the mileage your getting I can't offer any possible reasons why.

To correctly calculate it you need to fill the tank up and reset the tripmeter.
Drive until the tank is nearly empty, then fill it up again.
The amount of fuel it takes to fill it up, and the distance covered from the tip meter are what you use to calculate the mileage.



Doing it the way you have done it leaves a huge margin of error.

Enough of an error, that when combined with other potential reasons accounts for your variation from the standard 20mpg.

Ok your very confusing. That is the way I have been calculating it. I fill the tank up drive to its nearly on empty. Take the amount it took to fill it and divide it by the miles drove on the trip meter. I know how to calculate mileage, its not rocket science its basic math. You're making it rocket science. Please dont post a reply if your going to keep telling me basically I don't know how to do basic math. Let someone else help me. Thanks for the math lesson.

This:

Ok, at last fill up it took around 16.5 gallons. The fuel gauge is on quarter of a tank right now, and I have drove 250 miles.

Is not the same as:

I fill the tank up drive to its nearly on empty. Take the amount it took to fill it and divide it by the miles drove on the trip meter.



But, never mind.
We'll assume the 15mpg you calculated was done correctly.


Tech II has pointed out that the Aztek is only rated at between 17 and 24mpg depending on how it is being driven.

Your 15mpg is quite close to the lowest possible, what sort of conditions were you driving in?
Approximate average speeds, city, ubran or highway, how many people in the car etc?

I basically like to do the estimate over the course of like 3-4 fillups, to get a better idea of the true mileage....

24/17 or 20 combined is for a new vehicle that is running at peak efficiency....your vehicle is 8 years old....I don't believe you gave the mileage.....but if it has a lot of mileage, those numbers will probably drop.....

As Moppie was saying, how you drive and under what conditions it is driven come into play here......Do you accelerate fast? Are you a lead foot? Tail gater? is most of your driving local or highway? Do you drive in a hilly area?

Condition of engine/transmission/tires? All factor in on your mileage.....

Its my wife's car. I understand what moppie was saying, but I have monitored the gas mileage for the past few months. It doesn't seem to be any different if its highway or city driving. When I say city driving its not like big cities, with a light every block, but kinda like back roads. Speeds are anywhere between 35 in town where we live to 55. My wife seems to drive normal when I'm with her, but we all know how most women drive. I've had to keep on telling her to stop completely before shifting from reverse to drive, lol. Most of the time she is by herself driving, the car has brand new tires on it. I clean the iac and throttle body regularly. As I said before the plugs and wires haven't been changed in two years, but everything else has been changed. I would have to say she doesn't have a leadfoot, and she definetly isn't a tailgater, just flighty sometimes. I know the car has alot of miles on it, but it just seems it should get better mileage. I had a 1994 grand prix with a 3.1 sfi, almost same motor as this car and it had 200,000 miles on it and it got way better mileage than the aztek. But I know there would be a difference in between the aztek and the grand prix, because the aztek is more of a van or small suv than a car. Thank you guys I do appreciate it. Moppie sorry for being kinda of difficult, :)

Also no hills around where we live or drive, and she accelerates normal, not fast or super slow.

try o2 sensor

Did you put your air filter in correctly? It's pretty difficult to replace the air filter without taking the intake hose off at the plenum. I changed my filter out last year and fought with the replacement all the way, squeezing it into the air box without removing the front cover assembly completely. Bruised and bloodied because I did not latch the bottom of the air box cover correctly I paid for my mistake further with the loss of mileage Now that I'm a little older and a little wiser I've resolved to trying to do things the right way. Last week I changed the filter out again, this time with a K&N. As there was no way I was going to ruin a fifty dollar filter by trying to squeeze it into place I took the hose off at the plenum this time. It was still a bitch but at least I knew my air box was locked up tightly, the way its supposed to be. Since the change out, I've noticed a slight increase in mileage. Not much, probably because of the winter blend of fuel we get here in n.e. Ohio, but a bit. Also, if you ever notice your mileage drop after a tank fill-up, suspect water in the gas. Now back to the way you drive and how to figure your mileage before I can answer your question and the need to know the weight and ages of all the passengers in your car and blah, blah, blah. Hope this helped. :grinyes:

This post is over a year old......

Vpedwards, be careful with the K&N filters......they are ok, but be careful not to over oil them, because the oil can contaminate the MAF sensor....