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Discussion Starter · #1 ·
Hi everyone!

I need some help... I just got my 2012 Mazda3 SA Grand Touring, and although I'm in love with the car (more bells and whistles than I would've ever needed...cool!), I'm struggling with the gas milage on the car.

By specs, the car should be getting 28mpg city, just like my previous Mazda2. I used to get exactly that milage out of my Mazda2, 28mpg in the city. I'm a bit on the heavy foot side, but still got very good milage with the Mazda2, so my driving behaviour has not changed. I drive the same segments as well, low to mid traffic areas.

I'm getting 22mpg from the Mazda3 SA. My friends 2008 2.3L Mazda3 gets that. Another pals 2011 Mazda 3 2.5L gets 19-20mpg. A couple of other 2012-2013 Mazda 3 SkyActiv owners living nearby are getting between 29 and 33 mpg in average.

I'm just puzzled. I can accept that a car won't meet it's EPA by a margin, but that's almost 30% more consumption than what it's rated for.

So far, I've swapped air (K&N now) and oil filters, oil, sea foamed it and cleaned the MAF sensor. I'm looking to change the sparkplugs since per my mechanic, they seemed worn and were the original ones (50k+ miles on them) and clean the throttle body. Using the rated 86 octane regular fuel, tire pressure correctly at 36lbs (R17).

I'm looking for a bit of guidance. Anything I should be checking or cleaning or doing to rule out? The margin is so big, that I'm thinking something is just downright failing.

Below is the general info from my OBDII reader. I don't have much knowledge on using these, so I'm not sure what to look at and what is right and what is not. I was told to check the Short and Long Fuel Trim reads, but can't find them in the Torque app, or don't know what they're called. Car was Parked with Hand brake on. Speed at 4 km/h, Load at 31% and throttle at 12.9% catch my attention, since it's parked and not moving.



Thank you.
 

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Spark plugs could be a big part of that, but I only get about 27, 28mpg when driving in the city, myself. And that's shifting at 3000-3500rpms when I'm hypermiling.
 

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Discussion Starter · #3 ·
Here's hoping... I'm really hoping to get it sorted out. The car is awesome, but it's just drinking up the gas tank. I'll have the spark plugs, which took forever to find good replacement ones, next week.

Anything I should check in the meantime? Now that I have a OBDII reader, I think I may be able to troubleshoot it a bit deeper.
 

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An OBD2 reader won't really help much in this respect, as it can only read codes. If you have a bluetooth OBD2 reader and an app on your phone to read it, like Torque, you can see what the engine is doing, which can help track down possible issues if you know how to read the data.
 

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Discussion Starter · #5 ·
I got a bluetooth reader, and use the Torque app on my cell phone. Data off the engine is above the screenshot. I confirmed again, throttle is always "stuck" at 13% - 16%, even if car is parked. Is this normal? Should it not be 0% if I'm not pressing the gas pedal?
 

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Your throttle won't be at 0%. If it were, no air would get in and the engine would stall. I don't know what percentage it should be open at idle, though.
 

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Discussion Starter · #7 ·
That makes sense, thank you. I'm trying to figure out what could be wrong using this thing, which I have close to no experience with. Anything else I shoudl check?
 

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im assuming thats the fuel trim on the bottom. is that long term or short term? by what it says, i looks like you are running rich. so your car thinks it running lean and dumping more fuel.

and is that your load% at idle with nothing on?
 

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Lol I say your just really heavy foot. Mazda3 SA is not the same as the mazda2 engine. You gotta learn to be light on the gas... after I got the ms3 midpipe on my car barely hit 30s lol not unless I do long drive and being really light on the pedal. Right now I average 24-27mpg.
 

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Discussion Starter · #10 ·
im assuming thats the fuel trim on the bottom. is that long term or short term? by what it says, i looks like you are running rich. so your car thinks it running lean and dumping more fuel.

and is that your load% at idle with nothing on?
Yes, that is the load it was showing with the car parked, turned on, hand brake on. Not pushing the gas pedal. Could it reflect any issues there?

The bottom "Fuel" info seems to be the fuel remaining on the tank. At that time it was almost empty, two days ago with half a tank, it was at 56%. I can;t figure out how to show STFT or LTFT in this Torque app...
 

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Discussion Starter · #11 ·
Here are the STFT and LTFT, measured throughout a short 15 minute drive. As you can see from the min and max values listed, they both jumped around quite a bit. I was under the idea that the LTFT shouldn't move much??



And a couple of "tests" that failed per the Torque app, but have found no information on what they mean.



Help?
 

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Did you find the fix to the mpg problem. I have a 2012 with 86,000 miles and getting 20 in the city. I have had the Spark plugs replaced at the dealer and got new tires.
 
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