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Discussion Starter #1 (Edited)
The wife filled up her car today. It only took a little over 8 gallons with 25 miles showing on the range.

She didn't think it filled. So she did 3 more clicks of the fill nozzle.

When she got into the car, the range was only 335 miles; whereas, it normally shows close to 425 miles after a fillup.

It obviously did not fill.

Anyone else have this happen?

I finally have her watching the range because she seems to ignore that little strip of a thing called a fuel gauge. I once got into the car, and the range showed 0. I had no ideal when it zeroed; so I promptly put about a gallon of lawn mower gas into it to ensure I'd get to a station. After that, I had her reporting the range every day on a chart. She no longer does that, but she does watch the range.

Oh, it only took a little less than 8 1/2 gallons. Normally it takes near 10.

Ralph
 

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The fuel estimate is based on your driving behavior. It is not a fixed number per gallon of gas.

The car calculates your current average mpg based on your actual driving habits/driving conditions and uses that to calculate how many more miles you can go based on your current gas level.

For example, if I go on a long trip, keep the A/C off, keep the mph pretty constant and then get a full tank of gas, the car's mileage estimate will be 50-100 miles more per tank. I've had estimates as high as 338 miles for a 10 gallon tank and as low as 218 miles in a full tank.

Also, there is always room to top off a tank, but it really isn't worth it to do it normally. The potential to cause damage outweighs the benefits in my opinion.
CK
 
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Fuel Tank Size

The wife filled up her car today. It only took a little over 8 gallons with 25 miles showing on the range.

She didn't think it filled. So she did 3 more clicks of the fill nozzle.

When she got into the car, the range was only 335 miles; whereas, it normally shows close to 425 miles after a fillup.

It obviously did not fill.

Anyone else have this happen?

I finally have her watching the range because she seems to ignore that little strip of a thing called a fuel gauge. I once got into the car, and the range showed 0. I had no ideal when it zeroed; so I promptly put about a gallon of lawn mower gas into it to ensure I'd get to a station. After that, I had her reporting the range every day on a chart. She no longer does that, but she does watch the range.

Ralph
There is also the probability that Mazda have built in a "Safety Margin" in the fuel gauge readings. I believe there is always a gallon left in the tank when it says empty, "So you don't run out", this means every Mazda driver is always carrying a spare gallon they don't know about. If you are the careful type who never lets the tank get too low, that's 2 or 3 gallons you are dragging up every hill for the life of your car!!!!!!! The correct solution, if Mazda don't trust us drivers, is to have a better warning system, my old cars had a red portion on the gauge, with today's info system we could have a warning system where you select your own milage/fuel remaining point you want a serious warning displayed on the screen, audio, horn, lights.
 

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Ralph, I've never had that happen with my '15.

It sounds like your wife found a nozzle that is too sensitive or a pump that is too fast and caused a blow-back, either of which can cause the pump to stop prematurely.

If it keeps happening with other nozzles and pumps, I'd look to see if the car's tank venting system has gotten clogged up with something.
 

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She also could have been parked on an incline while filling the tank, creating an air bubble in the tank.
 

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Slow fill gas tank

After the first auto shutoff I put in another gallon or so. This takes some practice and patience. You can hear the fuel getting close to the top. Too much will overflow. Too fast and you will get gasoline spit on you or dribbled down the fender.

Again. Go slowly or spill gas.
 

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Discussion Starter #7
She says she had it spit back at her one time (another time, but not this time).

I've never had it either spit back nor dribble down.

Ralph
 

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I went to the gas station yesterday and filled up my tank, or so I thought. When I got back in the car, the fuel gauge wasn't reading full. It still had one bar left to go until full. I had added 8.4 gallons of gas and still had some left in the tank when I had started.

I will try a second fill up next time and go slowly until I get a 2nd click off, just to see what difference it makes.

I've only had this 2018 GT3 for two weeks and I've felt like the tank wasn't fully filled on both of my trips to the gas station. My 2016 ST3 never had this issue.
CK
 

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I just filled up two days ago and had a similar experience. I had two bars left on the fuel gauge and the fuel light was on. When I filled up, the nozzle clicked off at 8.2 gallons. I then held the nozzle lever half way and was able to get almost an additional 3 gallons. I did not force the remaining three gallons, I just kept the nozzle steady until it clicked off a second time. My cruising range estimate after fillup was 465 miles. It was under 400 when it clicked off at 8 gallons.
 

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Discussion Starter #10
Wonder what's going on? I've never been able to control these new nozzles. They're either off or on, not any feathering allowed; it seems.

They do have 2 or 3 ratchet stops though. Maybe filling using the lower ratchet stop might work better?

Ralph
 

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Wonder what's going on? I've never been able to control these new nozzles. They're either off or on, not any feathering allowed; it seems.

They do have 2 or 3 ratchet stops though. Maybe filling using the lower ratchet stop might work better?

Ralph
For the pumps that have it, I use a lower ratchet to fill the tank the rest of the way. Most of the pumps around here I am able to slow fill by hand.
 

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OK.. so I filled up my gas tank until the nozzle stopped yesterday. I then did a second slow fill by hand until the nozzle clicked off again.

When I get back in my car the tank gauge read full this time, which was good, and the mileage estimate was considerably higher than normal.

But after driving only 14 miles (half a gallon or so) my fuel gauge is already reading one bar down... very strange.
CK
 

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I have the same issue. I can usually get another 1.5 gallons in after the first click sometimes more. I did have one time where the fuel spilled over.
 

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I have been able to add as much as 1.3 gallons after the first pump shut-off. Probably could put more because I'm never gone to the point where gas spills out.

Given this ambiguity, I believe that one can never accurately measure how much gas was used, therefore mileage calculations "by hand" can't be too precise. The computer's calcs have been within 0.2 mpg of my hand calcs. Close enough that I don't bother doing hand calcs anymore.

But what I've observed, when the DTE says 0 miles, I can put about 11.5 gallons in the tank. That means with a 13.2 gallon tank, there is about 1.7 gallons remaining in the tank when the DTE hits zero. Approx 56 miles left (using my average of 33mpg).

I still try to fill-up when the DTE approaches zero, but good to know there are a few miles of safety left.
 

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Discussion Starter #15
Yes, you'll have maybe 60 to 80 miles left when the range is on zero.

Unless you're driving it when it hits zero, you have no idea where it is then. The fuel gauge will be zero. Range is zero. You have to see where an odometer reading is when the range goes to zero to know how many miles you may have left.

Running the car below 0 range may overheat the fuel pump that is in the tank, as it uses fuel to cool it off.

Ralph
 

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This is more of a problem with the gas pump than the car. In states that require vapor recovery gas pump nozzles, which is pretty much everywhere these days, the pumps tend to shut themselves down prematurely. Not exactly sure why, but I suspect it has a lot to do with the vapor pressure of the fuel, ambient temperature and the physical design of the car's tank/fill plumbing, as the condition varies depending on the temperature and which car I'm filling up.

Anyway, I've found that if I use the lowest pump speed setting on the nozzle, it gets pretty close to full - the higher the ambient temp, the less full it gets. Then I give it a few seconds for the fuel to settle in the tank before starting the pump again. Rinse & repeat, and you'll get the tank completely full.
 
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