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Hi, my boyfriend and I recently purchased a 2008 Mazda 3 hatchback. It has a 2.3 liter engine. Its gas tank is 14.5 gallons and it is supposed to get 22 mpg in the city and 29 mpg on the highway. The gas mileage seems to be okay in the city but on the highway it seems to go through more gas than it should. We drove to lansing and back which is about 40 miles there and 40 miles back taking the highway all the way there and back. When we got home we had like 2 notches above half a tank. That means it used like 6 gallons of gas when it should have only taken like 4 gallons of gas. Also, when driving on the highway it rides at 3,000 rpms. What could be causing it to use a lot of gas on the highway? Could it just be because it has a smaller engine?
 

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WELCOME TO THE FORUM

Just to mention...it takes a few fill ups and old school pen to paper math to calculate the MPG. Anything less you are not really getting an idea of average MPG. Also if possible for better baseline information use the same fuel station,fuel type and pump to get your fuel millage calculation estimates.

This is all assuming that there is no mechanical condition that could lower the best MPG and also that all your tires have the proper pressure in them (see door jam for info).
 

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We only fill up at Shell and use the same fuel type every time. The gas mileage for driving on the high way just seems terrible. I just went and got the tires rotated the other day and I am pretty sure they checked the time pressure. We also had an oil change like a week or week and a half ago. I am not sure what other services have been performed on it. We are going to try some fuel injector cleaner to see if that helps at all. We are trying to figure out if there is something wrong with it but we do have a 2 year warranty on it if there is something wrong with it.
 

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The SHELL fuel you use already has a fuel injection chemical additive that is added to the final retail product. Adding more serves only to lighten your pocket book.
 

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Well I think there might be something wrong with it because it shouldn’t take that much gas driving on the highway going that distance. We have a few other things that we are going to have looked at and done if the fuel injector cleaner doesnt do anything.
 

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Well I think there might be something wrong with it because it shouldn’t take that much gas driving on the highway going that distance. We have a few other things that we are going to have looked at and done if the fuel injector cleaner doesn't do anything.
Good!

and

Good Luck!
 

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Well I think there might be something wrong with it because it shouldn’t take that much gas driving on the highway going that distance. We have a few other things that we are going to have looked at and done if the fuel injector cleaner doesnt do anything.
The thing here is you don't really know how much fuel you used. There is no guarantee on the accuracy of the fuel gauge. Unless you recorded the actual mileage to and from and then checked the total amount of fuel used on the trip by filling the tank after, its just speculation.
Also, that 29 mpg might be a bit idealistic. If driven at 70+ mph or with a heavy foot, its not going to be close to that.
Don't go throwing money at the car to solve problems that may not exist. Drive it, record mileage and fill-ups, get an idea of actual average fuel consumption first, then if its ridiculously low get it checked.
 

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Well I know for sure that it shouldn't have used half a tank of gas just to go to lansing and back. Plus, I have no idea if it has had its regular maintenance done by the previous owners so it could need something done to it. The carfax didn't show anything done to it from 2010 until it arrived to the dealership where we got it from this year. Plus, I just took it to get the tires rotated and they said one of the rims was bent but said it was fine. However, we are going to get a new rim for it. I feel that it may need a tune up or something simple done it so we are going to take it step by step. We just used some fuel injector cleaner and then filled up the gas tank to see if that helps.
 

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"two notches above half a tank" means you don't actually know how much gas was used for your trip. Don't rely on your fuel gauge.

Start a trip with a full tank. After your trip, fill the tank back up to full. Then you know exactly how many miles you drove and how many gallons you used. If you do this 3 or 4 times you'll get a very good estimate of your fuel mileage. Doing it just once may be off a little bit depending on how "full" you really made the tank each time.
 

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Discussion Starter #11
I am not trying to see how much fuel it actual went through on the trip. We have driven to lansing and back many many times. We use to go to college there and drove there at least 2 days a week. I know for a fact it doesnt take half a tank of gas to go there and come back home. I just want to know why it went through more gas than it should have.
 

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I am not trying to see how much fuel it actual went through on the trip. We have driven to lansing and back many many times. We use to go to college there and drove there at least 2 days a week. I know for a fact it doesnt take half a tank of gas to go there and come back home. I just want to know why it went through more gas than it should have.

You made the trip many times, but not in this car.....
How do you know it used more gas than it should have if you don't know how much it actually used?
Again, you need to check actual mpg averages or you are just guessing.
 

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Hi, my boyfriend and I recently purchased a 2008 Mazda 3 hatchback. It has a 2.3 liter engine. Its gas tank is 14.5 gallons and it is supposed to get 22 mpg in the city and 29 mpg on the highway... We drove to lansing and back which is about 40 miles there and 40 miles back taking the highway all the way there and back. When we got home we had like 2 notches above half a tank. That means it used like 6 gallons of gas when it should have only taken like 4 gallons of gas...
Hi and congrats on the car.
There has to be something screwy because if the above is true, then you got about 13 MPG for that highway trip (80 miles / 6 gallons) and that's just crazy for that car/engine! Had it been 4 gallons, that's 20 MPG and even that is a bit low for that car on the highway.
My best friend recently traded in his 2007 Mazda 3 Hatchback and he raved about the MPG. I mean my previous car was a 2007 Mazdaspeed 6 (2.3L + turbo) and I got around 20-24 MPG combined city/highway and that was with a HEAVY foot! Sometimes I would even hit 26+ MPG on a long highway trip.

Like others have mentioned, you're going to have to approach this the old-fashioned way in order to rule some things out. Fill up every time and keep track of the gallons needed to get you back to full and the miles between fill-ups. Divide those miles by the gallons and that will give you a more realistic real-world representation of your MPG. That would also rule out a malfuntion with the fuel guage, which could be giving you a false reading.
If the old-fashioned way still produces MPG below 20 or so, then you'll have to look at other factors, including the possibilty of a leak in your fuel tank. Sounds far-fetched, but I have heard of this happening and that would definitely contribute to lower-than-expected gas mileage numbers. Hopefully it's a simple fix.

I'm interested in hearing what kinds of numbers you come up with after a couple of fill-ups.
Keep us posted and good luck!
 

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Driver Information System (DIS)

P.S. - I found something on a very old post (different forum) that might be of interest:


Driver Information System (DIS)

The audio system including factory in-dash CD changer apparently came in two configurations, one with DIS and one without DIS. The DIS includes: current fuel economy, average fuel economy, approx. distance you can travel on the available fuel, and average vehicle speed. It is accessed by pressing/holding the “INFO” button for about 3 seconds. This is supposed to work on some 2008+ models.

So basically, if your vehicle is equipped with an "INFO" button, it probably came from the factory with a trip computer built in. Check your owners manual for details.
If your vehicle has the clock adjustment button ":00" instead, then it does not have the hardware for the DIS.

In summary:
Push and hold the "INFO" button for about 3 seconds, then release. The display should change from Clock mode to Trip Computer mode, or DIS as Mazda calls it. I imagine that once you're in DIS mode, you just press "INFO" to switch between the different values.

***NOTE: The ignition switch must be in the ON position.***
 

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I have a 2015 Mazda 3 and it has the info computer that gives mileage info for trip average as well as tank average. These numbers are a guide as to the mileage you get, but as mentioned before, the old fashioned method of dividing miles driven by gallons used works every time and from my experience, varies greatly from the info computer. One caveat about the "old fashioned" method is that you have to fill the tank to the same level every time you fill or the numbers come out funny. I usually go until the pump clicks the off first time. Incidentally, I get 35-40 m.p.g. averaging 65 on the highway with 80% highway 20% city driving.
 

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I am not trying to see how much fuel it actual went through on the trip. We have driven to lansing and back many many times. We use to go to college there and drove there at least 2 days a week. I know for a fact it doesnt take half a tank of gas to go there and come back home. I just want to know why it went through more gas than it should have.
willettemily, with all due respect, please stop saying things like "I know for a fact" when you have no facts. Estimating gallons of fuel usage on the fuel gauge of a car you only recently bought is NOT a way to gather facts.

Please do what several people have already asked you to do. Fill up the tank to the very brim and jot down the mileage. Then do some driving (either that day, or over a few days). Then go back to that same pump and fill the tank to the very brim and jot down both the mileage AND the number of gallons you put in. Mileage = miles divided by gallons. Then repeat it once or twice more. Then average the several mpg numbers together.

THEN re-post on this (or any) forum with actual facts. I'm not being mean or whatever, and no one is saying your car is fine. What we're saying is fuel gauges are only a very rough approximation of gallons in the tank, and it's just a waste of time to either get worried or to start looking for causes of a problem you may not actually have.

Just do it the right way and then let's talk.
 

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Fill the tank up, reset trip odometer, take another highway only trip again, fill car back up, divide mileage by gallons used, i.e., 130 miles divided by 5 gallons would be 26 MPG. That's the most accurate way to do it.
 

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I also recommend monitoring your fuel economy first. I use www.fuelly.com to track my fuel economy. I basically just text my odometer reading, price per gallon, gallons filled and optionally my average speed for the tank and I get texted back with the mpg for the tank. The website has all kinds of graphs also.

On the freeway do you guys average about 65 or more like 85 mph? That kind of thing can make a huge difference. I assume windows are closed and you don't have anything on the car that would add extra drag
 

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When I bought my used 2008 Mazda 3 Sport 2.3L 5-door (automatic), I had a similar reaction. I had just traded in an Audi TT 3.2L (V6) for it. It was about a 45 mile drive home...mostly highway. I don't remember if the tank was 100% full from the dealership I bought it from but by the time I got home the fuel gauge was down more than a 1/4 tank. It was really peppy on the highway and I was driving it like my Audi....hard...just to see how responsive it was. Zoom Zoom right!?

By the time the tank was empty, I had barely driven 200 miles . I thought that couldn't be right...I was expecting the 22/29 MPG that you see on Edmunds.com. In the weeks/months after purchasing the car, I was on sites like this trying to figure out what was "wrong" with my car. I replaced the spark plugs, changed the air filter, cleaned the PCV valve, gave it an oil change, put in bottles of fuel injection cleaner, inflated my tires a few PSI above recommended, etc. None of that seemed to do much for me. I was still only getting roughly 20MPG.

It wasn't until I had to travel to Delaware for work that I decided this was the best time to test how much MPG I could get if I stuck to the speed limit and drove pretty much like a grandma...no jack rabbit starts, no revving past 3K RPMs and staying at 65 MPH on the highway. I was surprised that I got almost 320 miles out of the tank of gas...I think I drove it until the orange gas light came on. That was almost 27 MPG which was wayyyy better than anything I had ever gotten with city/highway driving back home.

I realized after that trip that how hard you drive really matters. I drive 50 miles roundtrip everyday for the past year and a half now and if I drive like a sane person, I can get roughly 240-250 miles per fill-up. I usually still have a little less than a 1/4 tank left at fill-up. But normally, I don't drive like a sane person and I do punch it at lights and do 75-80 on open stretches of highway. I do try to keep the RPMs below 3K if I can which seems to help...at 80MPH, the tach is a little above 3K and I can see that if I drive longer stretches at that speed, the needle on the gas gauge seems to go down much quicker.

So my advice to you is to let off on the lead foot and you will see your gas mileage get better.

Good luck!
 
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