[zero_gravity]

that's definitely a little high. despite what people tell you, the filters don't really have much of any effect on fuel economy. they might if they were REALLY trashed but that would take a lot. filters used to have an effect with carburetors but as soon as we started using fuel injection and sensors got better, all that happens is you lose some power in the higher RPM range.

worth knowing if you have manual or auto trans. tell us if there is anything unusual going on. noises? strange behavior? have you checked for ECU codes? any mods we should know about?

you're generally looking for anything that would waste engine power. a slipping belt, dragging brakes (the rear calipers are known to seize), fuel leak, misfires just to name a few. whats your mileage? was regular maintenance kept up? badly worn spark plugs could be a problem.

although very unlikely, the intake valves could be getting clogged up with carbon. i would leave that to last on the list to check. it's not really a problem on these cars but is not impossible. i'd guess usually with only driving short trips in the city would this ever be a problem and even then that would be rare.

give us all the information you can in as much detail as you can. fuel economy problems are difficult to sort out.

 

[zero_gravity]

Actually a few days ago I noticed that the car is pulling to the left, it might be a seized break caliper but it also can be just a bad alignment, I will definitely check both of those as soon as possible.

For more details I can add that my Mazda came with automatic transmission. Before I bought this car I check it in local Mazda service, there were no ECU codes. Mechanics listened to the engine, they didn't hear anything strange neither, everything seemed fine. The car has 50 000 miles on it and as I said, I bought it a week ago so I didn't really maintained it yet, but last owner did every maintenance it needed, everything was checked and changed regularly.
P.S. It doesn't have any mods installed, everything is stock. It's just a car for everyday driving, which gets 15mpg in the city)).

that would be a classic symptom of a seized caliper. if you put your hand near the wheels (don't touch!) after a 15 minute drive i'm going to guess one will feel hot.

if you find this is the case, here's some info. feel free to pass this on to your mechanic if you're not doing the work yourself. this is IF it is a rear caliper seizing.

- there's a recall for the parking brake. the cable that actuates the calipers has a rubber boot at the caliper end. the original boot can leak, make sure this recall has been done as it can cause a caliper to seize

- the rear brakes like to jam up anyway. root cause is corrosion buildup UNDER the pad shims. this pinches the pads and causes them to seize. this is not to say that other causes such as stuck slide pin or stuck piston shouldn't be investigated. fixing it is actually pretty easy. knock the pads out, you'll probably have to pound them with a hammer. before installing new pads/shims, use a heavy metal file (bastard file) on the channels where the shims go and the pad tabs ride. your goal should be to widen them a little. the corrosion has to be removed anyhow. next put a light coat of caliper grease there before putting the shims in. this will help prevent future corrosion and give it some room if it does start to form.

if it turns out not to be brakes, we can start exploring other possibilities. i'm not expecting much since you have no CEL. modern ECUs are very good and picking up small faults.

 

[zero_gravity]

I need some pointers as well. 2014 Mazda 3 2.0.

180km on the clock.

MAF + throttle body cleaned, new air filter and spark plugs listed on the manual.

The only thing not done is the cleaning of the intake valves, could that be it?


Mines a lot worse.
View attachment 298545

so converting that you're getting around 11L/100km. i get about 7, but that's almost entirely highway. it does get better if i slow down, even under 6.

seems so far you're throwing everything at the wall to see what sticks. this is a terrible way to solve your problem.

with intake valves, its possible but highly unlikely. although our motors are direct injecton they're not like the early ones at all. we have no way of knowing if it is the intake valves without more information and eliminating other possibilities. read my old thread here for more info: https://www.mazda3revolution.com/threads/intake-valve-carbon-investigation.235229/

first thing is what is your highway/city driving split like? if you're predominately city, your fuel economy is not going to be great and that is normal.

you've done the plugs, ensure they're the right ones. our motors require iridium plugs and they're not cheap at about $20/plug give or take. where were they purchased? we have seen counterfeit plugs here before.

air filter doesn't affect fuel economy, only power. cleaning MAF and TB likely not required nor will it help. if it does it may be a sign that something else is going on. sticking brakes....let me guess, mexico built and it was the rear brakes? we can talk more about that one...

getting ECU data would be helpful as well as any other possible symptoms. CEL or not, a code scanner is required to check for logged codes at the very least. things like O2 sensor data would be helpful.

how about an exhaust leak? the flex pipe can break (for example) and that will have an effect. thermostat stuck open would take far longer to warm up the motor, or may not warm up fully at all. so many options.

more info is better.

 

[zero_gravity]

LTFT seems fine....intake problem would include loss of power. significantly so. our cars build up hard carbon and not a lot of it. it needs to be picked out, the blasting will only do so much. we did have a member who soaked the valves in something like carb cleaner. the intake cleaning chemicals you spray in while the motor runs will not help carbon buildup.

that being said, you're wasting your money with the intake carbon but hey it's yours to waste.

by "bulletin rear brake job" i can only assume you mean the recall from...years ago. a service bulletin and recall are very different things. the recall was the boots on the rear parking brake cable. they didn't seal right and could cause the caliper to seize. if corroded, you're going to get to calipers. HOWEVER.....this is not the issue i speak of in my previous reply. read this one: https://www.mazda3revolution.com/threads/how-to-solve-rear-brakes-seizing.239565/unread

the result of that was instead of my rear brakes lasting only about 45k kms they now last over 120k kms. that is not a typo.

what was the previous mileage you had with this? if you're mostly in the city, your numbers aren't bad at all.

just a fun one, here's how to fix the nasty stains down the side of the front doors from the mirrors. it's a mexico thing. https://www.mazda3revolution.com/threads/how-to-fix-white-stains-from-the-side-mirrors.241270/unread