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M3TH (Mazda 3 Turbo Hatchback 2021) Polymetal Grey PP
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Discussion Starter #1
Been using the CX30 since Saturday and I just noticed that with my daily route I average 26-29mpg on SPORT mode all the time, while M3TH is around 22-24mpg only non sport mode. Aside from this the voltage reading while running for the CX30 is 13.7 while the M3TH is only 12.4. The M3TH doesn't have any problem cranking in the morning will all the heaters, defoggers, stirring wheel and seat heater at max setting. Normal or something to be concerned of?
 

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Hmmm....seems low voltage issues are becoming a common complaint with the new Mazda 3...12.4v is what the battery should be at when not being charged, ie with the motor shut off. 13-14v is what it should be when the engine is running and the battery is charging. Maybe you should check the battery with a DVOM and see if it reads the same.
 

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M3TH (Mazda 3 Turbo Hatchback 2021) Polymetal Grey PP
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Discussion Starter #3
My M3TH is at the dealership for the Keyless entry fix. Might as well have them look at this issue. The mpg makes me a tiny bit envious, lol
 

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Somehow this doesn't surprise me. Yesterday I had to jump start after testing the new amp for only 5 MINUTES! Thinking of adding a capacitor maybe. Anyone know if that should help? I know I can get a second battery or upgraded alternator, but I'd rather avoid that if possible. The amp's average current draw is only 75 Amps.
 

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M3TH (Mazda 3 Turbo Hatchback 2021) Polymetal Grey PP
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Discussion Starter #6
I initially told the service guy at the dealership about my voltage remaining 12.2 or 12.4 even when the car is running. Je said your car is a 12 volt system..... not buying it so far. At least he said he will look in to it. I will test the same year and model at the dealership if they do have 12.2 volts only.
 

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Yes, of course its a 12v system, just as almost every car made in the past 50 years. The battery should have a nominal charge of ~12.5 volts to start the engine and run the electronics but a charge current of ~14v from the alternator is needed to keep the battery charged and still run all the electronics. Unless Mazda is doing some trickery with the charging system and only supplying a charge to the battery when needed, that person at the dealer needs some basic training on how cars work.......
 

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I have 2,100+ miles on my 21 M3TH and I can’t seem to get above 22mpg a tank no matter what I do. If I drive with a heavy foot I get 19mpg if I feather it and do highway driving with minimal city I still get 22mpg. I wonder if Mazda got the tuning wrong for it. I’m hoping they look into the abysmal mpg because I’m getting nowhere near the stated amount. I’d get it if I was driving an SUV but this has been ridiculous. I got better gas mileage out of my 05 IS300 with the same driving style. I can’t get more than 200miles from F to E so it’s maddening
 

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M3TH (Mazda 3 Turbo Hatchback 2021) Polymetal Grey PP
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Discussion Starter #9
Yes, of course its a 12v system, just as almost every car made in the past 50 years. The battery should have a nominal charge of ~12.5 volts to start the engine and run the electronics but a charge current of ~14v from the alternator is needed to keep the battery charged and still run all the electronics. Unless Mazda is doing some trickery with the charging system and only supplying a charge to the battery when needed, that person at the dealer needs some basic training on how cars work.......
Don't worry I am going to check the voltage of other M3TH at the dealership before I take back my car.
@PRMANManman
Yes 19 to 22/23mpg. This CX30 non turbo has been running 27mpg since I have been running this on sports mode since yesterday.
 

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M3TH (Mazda 3 Turbo Hatchback 2021) Polymetal Grey PP
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Discussion Starter #10
Spoke with the tech the front USB is constant 12.2 or something when car is running. The CIG lighter socket does charge to 13-14 when car is running. This was confirmed as I even tried this on their units.
The CX30 2021 non-turbo gave 26-27 mpg on sports mode aggressive driving the entire 2 days . My M3TH on pamper kid mode driving 22-24 mpg. I just got my M3TH back today.
 

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The draw is 75A or 7.5A. If it's really 75A, I don't think my battery would start after 5 minutes either.
Definitely 75A. Upon further reflection, I think I'll need a second battery so I don't have to idle while listening, which I'd rather avoid. Happened again today unfortunately.
 

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Unless Mazda is doing some trickery with the charging system and only supplying a charge to the battery when needed
That just might turn out to be spot on, or close enough, and it would help explain why they've been so sensitive...
 

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I have 2,100+ miles on my 21 M3TH and I can’t seem to get above 22mpg a tank no matter what I do. If I drive with a heavy foot I get 19mpg if I feather it and do highway driving with minimal city I still get 22mpg. I wonder if Mazda got the tuning wrong for it. I’m hoping they look into the abysmal mpg because I’m getting nowhere near the stated amount. I’d get it if I was driving an SUV but this has been ridiculous. I got better gas mileage out of my 05 IS300 with the same driving style. I can’t get more than 200miles from F to E so it’s maddening
You’re getting better MPG than me. I’m lucky for a single drive to hit 20MPG, my average is up to 17.1 now but ripping it I get 9MPG (not instant MOG, my average will actually drop to 9)
 

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You’re getting better MPG than me. I’m lucky for a single drive to hit 20MPG, my average is up to 17.1 now but ripping it I get 9MPG (not instant MOG, my average will actually drop to 9)
I just traveled this morning from Baltimore to nyc on the 95 and I could only eek out 25mpg. Cruising at 80mph gets me only 22 instant mpg. Of course I wish it got better mpg but my complaint is the size of the tank. Filling up every 200 miles is pretty annoying.
 

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People with the Mazda6 turbo aren't getting particularly poor gas mileage. Not AWD... but the 3 has less frontal area and is a smidgeon lighter. AWD mebe takes a bunch 'o fuel?
 

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M3TH (Mazda 3 Turbo Hatchback 2021) Polymetal Grey PP
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Discussion Starter #17
@PRMANManman
The CX30 non-turbo and M3TH has the same gas tank size but with the CX30 fuel mileage it would be lesser gas fill up on the that Baltimore-NYC trip. We also do that trip every other month.
 
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