Has anyone had this fuel gauge problem

2018 grand touring. Tank was at 1/4 so I stopped and filled it up. After fill up the gauge still read 1/4. Went back to the station and "topped it off" (it took two dollars). This week as I travel to work, the gauge has run itself to empty. Any ideas?
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg. Plano, TX
Contributor
:
Plano, Texas, USA
2018 grand touring. Tank was at 1/4 so I stopped and filled it up. After fill up the gauge still read 1/4. Went back to the station and "topped it off" (it took two dollars). This week as I travel to work, the gauge has run itself to empty. Any ideas?
Usually this means the fuel gauge sending unit in the gas tank acting up. Take your 2018 CX-5 back to your Mazda dealer for warranty service.

Try to use Top-Tier gas all the time which may prevent this kind of problem happening.
 
Car is still under warranty. I have an appointment on Tuesday. I'll report back on the cause so you can refer to it if you have the same problem. As far as using top tier gas, I have to admit, it has not always been the case, but I think it might be time to stick to a brand name.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg. Plano, TX
Contributor
:
Plano, Texas, USA
Car is still under warranty. I have an appointment on Tuesday. I'll report back on the cause so you can refer to it if you have the same problem. As far as using top tier gas, I have to admit, it has not always been the case, but I think it might be time to stick to a brand name.
Yes, please report back to us after your dealer visit.

BTW, top-tier gas doesn’t have to be a name-brand. Although I use only Shell gas, but Costco gas is the top-tier gas with much better price.
 
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2018 CX5
Was it 1/4 down or at a 1/4 left? I have had this happen to me with other cars (Infiniti I30) when it was only down a 1/4 and I filled it up but not with the CX5 (also haven't tried to fill when only down a 1/4)
Let us know what the dealer stays!
 
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Occupied Calif.
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2019 CX 5 GT-R
Sticky floats/sending units are not unheard of these days due to the quality of some gas. I had a Nissan 370Z that sometimes wouldn't show as full even if the tank was filled to overflowing, which is not a good thing to do. The solution, as recommended by many members on the 370Z Forum was to add 6-8 oz. of Marvel Mystery Oil about every 3 or 4 tanks. It works. I now do the same think with my CX 5 and I only use top tier, Arco or Shell 91 octane. I would suggest running a couple of doses in the next two tankfuls. Don't add more than 8 oz. per tank. The mild solvent and lube properties of MMO seem to free up the floats.
 
Sticky floats/sending units are not unheard of these days due to the quality of some gas. I had a Nissan 370Z that sometimes wouldn't show as full even if the tank was filled to overflowing, which is not a good thing to do. The solution, as recommended by many members on the 370Z Forum was to add 6-8 oz. of Marvel Mystery Oil about every 3 or 4 tanks. It works. I now do the same think with my CX 5 and I only use top tier, Arco or Shell 91 octane. I would suggest running a couple of doses in the next two tankfuls. Don't add more than 8 oz. per tank. The mild solvent and lube properties of MMO seem to free up the floats.
Thanks for the advice. Interestingly, I had to fill the tank yesterday, and the gauge came all the way from empty to full. I wonder if there will be a code, or if my trip to the dealer will be for nothing.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg. Plano, TX
Contributor
:
Plano, Texas, USA
Thanks for the advice. Interestingly, I had to fill the tank yesterday, and the gauge came all the way from empty to full. I wonder if there will be a code, or if my trip to the dealer will be for nothing.
When it happened once, it may happen again at certain point in the future. If you took some pictures showing the problem, that should help. I don’t think there’s a code for this problem. But you should still go to the Mazda dealer for the problem, and hopefully they can find something although it’s unlikely at this point.

What kind of gas did you use for the last 2 or 3 refills? Although your symptom looks like the float level temporarily got stuck and somehow it loosed up in your last gas refill making your fuel gauge back to normal. But the float on the fuel gauge sending unit is very strong, getting stuck is unlikely to me. Most likely the variable resistor on sending unit is having bad connection for the contact, and sometimes good detergent gasoline may clean up the film on the variable resistor.
 
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2017 Mazda 6 Sport
This happened with my '17 Mazda 6 right after I bought it 3 years ago. It happened once, then never again
 
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2018 Cx-5 grand touring w/prem. pkg.
this is printed in owners manual

  • USE ONLY UNLEADED FUEL.
    Leaded fuel is harmful to the catalytic converter and oxygen sensors and will lead to deterioration of the emission control system and or failures.
  • The use of E10 fuel with 10 % ethanol in Europe is safe for your vehicle. Damage to your vehicle may occur when ethanol exceeds this recommendation.
  • Never add fuel system additives, otherwise the emission control system could be damaged. Consult an expert repairer, we recommend an Authorised Mazda Repairer for details.
 
When it happened once, it may happen again at certain point in the future. If you took some pictures showing the problem, that should help. I don’t think there’s a code for this problem. But you should still go to the Mazda dealer for the problem, and hopefully they can find something although it’s unlikely at this point.

What kind of gas did you use for the last 2 or 3 refills? Although your symptom looks like the float level temporarily got stuck and somehow it loosed up in your last gas refill making your fuel gauge back to normal. But the float on the fuel gauge sending unit is very strong, getting stuck is unlikely to me. Most likely the variable resistor on sending unit is having bad connection for the contact, and sometimes good detergent gasoline may clean up the film on the variable resistor.
I have been using pretty much the same fuel for three years, not a name brand. I think your suggestion about the resistor is on point. I'll be changing gas brands from now on.
 
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Occupied Calif.
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2019 CX 5 GT-R
this is printed in owners manual
  • Never add fuel system additives, otherwise the emission control system could be damaged. Consult an expert repairer, we recommend an Authorised Mazda Repairer for details.
This is typical owners manual boilerplate. The manufacturer's have no control over what or how much of a fuel additive that somebody may add to the tank. For example, someone may pour in a whole 32 oz bottle of MMO like you would with a bottle of Techron or Gumout. Or a quart of Acetone or entire bottle of octane additive.
Marvel Mystery Oil is a mild Stoddard solvent with some other lubricating additives.
Using 6-8 ounces per 16 gallon tank is safe. A quart of it is only about $6. Well worth a try to solve the problem and as a preventative maintenance dose every few tankfuls.
 
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