Severely inaccurate fuel gauge?

[icebalm]

I bought a 2012 GS-SKY in october, and it's been pretty sweet so far, but the fuel gauge is really weird. I've been tracking my fill ups on fuelly.com, and I've been resetting my trip counter between fill ups to see how many klicks I'm getting per tank.

I've noticed some really strange behavior with the fuel gauge. It is 12 squares separated into groups of three. With a 55L tank, each square should be about 4.6L. I've noticed that the top end of the gauge goes down slow, but the bottom end is super fast, some squares only last 30 KM (!). The past two fill ups I have only filled it up when it's on the last square and the low fuel light is on, and to top off my tank I have pumped in 41L, which means there was 14L still in the tank! The gauge should have still read 1/4 full.

What's going on?! Obviously with the gauge always reading much higher than normal I don't think I'll ever run out of gas, but it's so inaccurate as to be almost worthless.

[peterm15]

There will always be gas left in the tank. I call it the reserve ( probably not the right name. ) and I've always found cars do this. The first 1/2 of the tank lasts say 300km and the last part lasts like 200.

[Thrizzl3]

i get this too..i get my hopes up when i'm at 340kms at half tank..sweet 680 to a tank guaranteed! not even close...ends up being like 590-600...

[icebalm]

Well, with 14L left in the tank and the mileage I seem to be getting it seems weird to me that I could potentially drive it for almost 200 km with the low fuel light on...

[Thrizzl3]

when the fuel light first appears..how many kms do you do on average?

[Dynames]

This is completely normal. When I'm down to no squares left I still only fill up around 44L, therefore 11L in reserve.

[icebalm]

when the fuel light first appears..how many kms do you do on average?

About 530-560km.

[Thrizzl3]

probably still in break in period...

[trulankan]

About 530-560km.

thats really low for a skyactiv seeing what others get, maybe you are driving it hard? how many KMs have u put on it so far? i think it will improve after 15-20K (2-3 oil changes)

[eSS]

Happens to me as well with my Sky3. I usually average around 380-400kms and hit half tank. This will take me (depending on trips) anywhere between 680kms-720ish. With the colder weather setting in I'm averaging around 660km or so which isnt bad. Highest I got was 765kms. Same issue will fill up at around 40-41L.

I find though when I do fill up at the first click I wont lose a bar till maybe about 150km. Most I've gone was 183 and lost my first bar. I'd say wait till summer and it gets warmer. I only noticed this behaviour when it started to get colder

[dambay]

It's because the gas tank does not have a linear cross section. Likely closer to the bottom of the tank, the cross section gets smaller, and so the fuel level goes down quicker. Given that the gas gauge reads from a mechanical float, it will drop quicker towards the bottom of the tank, and so the gauge will not seem linear.

[thirdgen3]

Just wondering, when the last bar is visible and the gas light comes on...how far have you guys/gals gone on that? Last night I went 45km then got gas...I was too worried about running out. Just curious, that's all.

[kilo4321]

Also most modern day fuel tanks only allow an 85% fill up and this is due to the expansion of fuel as temperatures increase, as fuel can expand by up to 15% in volume with the correct temperature fluctuation. Thus if you have a 55L tank, the simple formula would be 55x 0.85 = 46.75 (or 55x 0.15 = 8.25L) So therefore 46.75L is the available amount of fuel you should be able to carry. The reason why most pumps say "corrected to 15 degrees Celsius" is because that is the optimal temperature to get the maximum amount of fuel storage out of their underground tanks -IIRC.
Hope that answers most of the head scratching.

[icebalm]

thats really low for a skyactiv seeing what others get, maybe you are driving it hard? how many KMs have u put on it so far? i think it will improve after 15-20K (2-3 oil changes)

I've been babying it. It's the first brand new car I've ever bought. I have 4300 km on it and I really hope this improves.

[icebalm]

Just wondering, when the last bar is visible and the gas light comes on...how far have you guys/gals gone on that? Last night I went 45km then got gas...I was too worried about running out. Just curious, that's all.

I've only gone about 35 km. Been too afraid of running out.

[kilo4321]

Just wondering, when the last bar is visible and the gas light comes on...how far have you guys/gals gone on that? Last night I went 45km then got gas...I was too worried about running out. Just curious, that's all.

Roughly 70k before I get nervous. The fuel gauge still goes down to zero squares displayed and continues to run for another 30ish Km city driving before I get paranoid. Never ran out of fuel before. Even if I do, Mazda roadside still can rescue my ass :)

[eSS]

Roughly 70k before I get nervous. The fuel gauge still goes down to zero squares displayed and continues to run for another 30ish Km city driving before I get paranoid. Never ran out of fuel before. Even if I do, Mazda roadside still can rescue my ass :)

When i hit my highest average at 765kms and the gas light came on I was contemplating trying to hit 800kms and then have road side save me. But I bitched out

[SonicBoy]

Did you see this thread post by Booter22? <link> (http://www.torontomazda3.ca/forum/showthread.php?67589-Dealer-Personalization-Options&p=1037206&viewfull=1#post1037206)

Could it be possible that this option has been set different than normal?

Fuel logic
Change fuel gauge needle speed correction.
Enabled
Disabled / Enabled

NOTE:

•Enabled: The fuel gauge adjusts the fuel gauge needle operation speed based on the fuel consumption amount signal input from the PCM via the CAN lines, and the fuel consumption amount sent from the fuel gauge sender unit.

•Disabled: The fuel gauge adjusts the fuel gauge needle operation speed based on the fuel consumption amount input from the fuel gauge sender unit.
Instrument cluster

[eSS]

Now that is interesting information!

[r4mi5awi]

Did you see this thread post by Booter22? <link> (http://www.torontomazda3.ca/forum/showthread.php?67589-Dealer-Personalization-Options&p=1037206&viewfull=1#post1037206)

Could it be possible that this option has been set different than normal?

Fuel logic
Change fuel gauge needle speed correction.
Enabled
Disabled / Enabled

NOTE:

•Enabled: The fuel gauge adjusts the fuel gauge needle operation speed based on the fuel consumption amount signal input from the PCM via the CAN lines, and the fuel consumption amount sent from the fuel gauge sender unit.

•Disabled: The fuel gauge adjusts the fuel gauge needle operation speed based on the fuel consumption amount input from the fuel gauge sender unit.
Instrument cluster


So which option is the better one? How do we go about changing these settings?

[dentinger]

It's because the gas tank does not have a linear cross section. Likely closer to the bottom of the tank, the cross section gets smaller, and so the fuel level goes down quicker. Given that the gas gauge reads from a mechanical float, it will drop quicker towards the bottom of the tank, and so the gauge will not seem linear.

bingo.

[killerbichon]

the sad fact of the matter is a skyactive won't add up economically taking gas into cosideraton versus a used mazda3speed. if you save 20 grand buying a used car thats lot of gas!!! It will take 50,000 litres of gas to equal that saving!

[peterm15]

the sad fact of the matter is a skyactive won't add up economically taking gas into cosideraton versus a used mazda3speed. if you save 20 grand buying a used car thats lot of gas!!! It will take 50,000 litres of gas to equal that saving!

I really think its time for you to drop the new vs used crap. People buy new. Get over it. You buying used doesn't make you any smarter. Why do you care so much.

[Booter22]

So which option is the better one? How do we go about changing these settings?

i only would suspect its under the personalization options. but i have never checked and i dont know if it makes any difference or what it may do when changed.

[Odin]

So what's the Budds Mazda policy on getting personalization options changed?

[icebalm]

the sad fact of the matter is a skyactive won't add up economically taking gas into cosideraton versus a used mazda3speed. if you save 20 grand buying a used car thats lot of gas!!! It will take 50,000 litres of gas to equal that saving!

Uh, I didn't even pay $20k for the car, lol.

[Paul17]

Its all not just the skys my 2011 gx does the same not sure

[2012speed3]

My speed is the same, supposed to be a 60L tank but even driving 30km beyond indicated range on 0 I can only squeeze 54L on the tank.