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Discussion Starter · #1 ·
Hi all! I've had my 2010 Mazda 3 with the 2.0 for about a year and I've noticed I get about 19 to 21 miles per gallon City. Has about 115,000 mi on it.
I recently bought NGK ruthenium spark plugs and denso ignition coils, which should get here on January 3rd.
I drive like an old man 95% of the time.
I maintain the oil and the air filter.
Bought a PCV valve but found that's almost impossible to change without a lengthy commitment so that's delayed.
What else can I do to try to improve the gas mileage? Is there anything not gas mileage related that you guys recommend I address soon?
Thanks much hive mind!
 

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remove any excess weight from the trunk
another few psi in the tyres
clean throttlebody and maf sensor
and as over 100,000 miles, recommend new quality O2 sensors
 

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Discussion Starter · #3 ·
remove any excess weight from the trunk
another few psi in the tyres
clean throttlebody and maf sensor
and as over 100,000 miles, recommend new quality O2 sensors
I've done /do all of that except replacement O2 sensors. That will have to be on my list next.
 

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Other than possibly the upstream O2 sensor (buy OEM or Denso), nothing. So far I'm not hearing anything which suggests your car is getting worse fuel economy than should be expected.
 

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Discussion Starter · #5 ·
Upstream O2 looks pretty easy to replace.

How many O2 sensors is on a 2010 Mazda 3? I know of the upstream and the downstream but is there one for each Bank either side of the catalytic converter?
 

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Just one upstream O2 sensor. Keep in mind, there is nothing you've posted so far which indicates your car has an issue, or, said another way, changing the O2 sensor, especially if you buy a Bosch unit, could possibly make things worse.
 

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Discussion Starter · #7 ·
I wouldn't use a Bosch, I would use an NGK, that is an OE part. The tank I just went through I got only 23. 6 miles per gallon and it was about 80% highway miles and I drive like an old man. It should be in the 30s from what I've seen. Poor gas mileage is something, if you fix problems while they're still in that stage you can usually stop them from becoming bigger problems, that's why I was asking.
 

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When it comes to fuel economy there really is no such a thing as "should be". FWIW, I bought a brand new 2009 Mazda3 with the 2.0 liter engine and a 5-Speed manual; back then my commute was about 80% highway and I don't believe I ever got more than about 28 mpg during my daily commute. On long duration road trips I was able to get the fuel economy up into the low to mid-30s, but that was the exception and not the rule.
 

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Are the SkyActiv engines that helpful? This is the kind of mileage I'm getting from my 2021 3 Turbo… Running 91 octane.
 

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Driving like an old man does not necessarily win a higher MPG. In fact, you may be lowering your MPG by that driving style. Aside from what was mentioned you need a gauge that can give you instant MPG read out so you can re-train your driving habits.
 
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