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when I fill up, it always say 400+ miles left no matter what the car computer said my previous mpg was.

So how is it calculated when I fill up?
 

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According to the 2017 manual (4-19 and 4-20):

If there is no past fuel economy information such as after first purchasing your vehicle or the information is deleted when the battery cables are disconnected, the actual distance-to empty/range may differ from the amount indicated.
I'm guessing that it stores your average over long periods of time unless it gets a hard reset via battery disconnect. I always soft reset my average through the computer after each fill up*, I don't know if this would affect it or not. My guess is that if it's designed well it will record the average MPG value at each soft reset (up to say 10 times or so) and then average that number to arrive at a mile range value. It would be cool if it weighted the "newest" MPG values in its calculation to give you a more accurate range but I doubt it.

*(which is somewhat pointless I guess since I have the infotainment app.)
 

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And a fun fact. Several members are balsy and hit the trip reset button when the Range hits 0 miles. They've confirm you can drive a good 40 - 50 miles before you actually run out of gas. I normally let my range hit 0 and then fill up. I don't take it much beyond that, but thanks to those members, I don't get nervous when I hit zero, I just know it's time to find a gas station.
 

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Further reading suggests that the data is in fact stored when the average MPG is reset via the Fuel Economy Monitor in the infotainment system, since it will graph the last values up to 5 resets. When reset it "syncs" with the in-dash average MPG and trip meters.

This is all theory for me—I've only filled up and reset the average once since getting my car.

(Sorry to double post, I can't find a way to edit my last post.)
 

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Note how quickly the system recalculates your range as it assesses your current driving conditions.

Sent from a Samsung that doesn't explode.
 

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I never seem to hit the estimated range before I fill up, but then I don't know how far I could drive after the low fuel light comes on. When I refill it will say perhaps 625 - 650 kms range, but I only hit perhaps 500 to 550 before the low fuel light comes on with mixed driving. Perhaps with 100% highway driving... I reset the trip meter at each refill (a habit from riding motorcycles without fuel gauges).
 

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Pretty sure it takes the avg mpg x tank volume filled. Ours shows anywhere between around 400 up to near 430.

I think the Range miles plus the miles I keep on one of the trip odos zeroed out every refill is a better indicator of mpg than the "avg mpg" value. The avg mpg tends to be pessimistically low by about 1 mpg. 40 mpg = 450 on Range + trip odo. Every 10 miles off this is about 0.9 mpg.

I've had the Range miles actually go up once it goes below 30 and the car is getting good mileage.

Best to fillup before the Range gets to zero because unless you've noted the miles on an odo at that point, you have no idea how much fuel you have left. Note the miles on an odo @ 0, then you have about 1.3 gallons left, or about 40-50 miles depending on your engine size, driving conditions, etc.

I backed out of the garage one morning and didn't note the Range until up the driveway. The Info had been moved to Avg Mpg. Moved it to Range, and it read zero. My wife had ignored both the fuel gauge and the fuel light, which comes on @ 30 on the Range. I immediately came back and got the lawn mower fuel out and emptied into the car, maybe a 1/2 gallon. Had enough to go to a service station then. I have her now watching the Range value since she ignores the fuel gauge. She's so used to looking at an analog fuel gauge, that this sliding scale one doesn't hit her eyes.

Ralph
 

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When the range hits 0, there's still three gallons left in the tank (during the summer or warmer months). That's almost a proven fact (see mpg thread). I've safely driven 78 miles past 0 and still had 0.8 gallons left (last summer). As it's gotten colder, mpg's has gone down so fill-ups at 0 has left me a gallon to two still in the tank. There's really no need to panic when it hits 0. I just drove from Washington DC to Annapolis (about 50 miles) last week starting the trip with 10 miles left on the range. I've gotten pretty comfortable with the refuel light, the "empty" tank gauge, and the 0 range. I'm just not a fan of refueling so quickly and with so much left in the tank. My old Mazda6's refuel light didn't come on until there was 1.2 gallons left and I took that to less than a gallon consistently. The manual says low fuel in the tank may cause damage to the fuel filter but I'm not sure how much merit there is to that.
 

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If you sync your avg mpg meter to your A trip meter, your avg mpg will be reset everytime you reset your A trip meter. The range (distance-to-empty mode)displays the approximate distance you can travel on the remaining fuel in the tank, based your current fuel economy. When the range meter is synced with the graduation marks on the fuel gauge. When all fuel gauge marks are gone, the range should read 0. However, when my gauge says empty and the range says 0, I can travel 72 miles (hwy) before running out of gas. Whenever I get a vehicle, that is the first thing I check, the miles I can travel when the gauge says empty and actual empty. Also, the owner's manual does say to refuel as soon as the low fuel warning light comes on. It's your call on that. IMO, there is less chance of gunk build up, the lower you let the fuel get in the tank. Some say the fuel pump could overheat doing that. I disagree.
 

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When I refueled just after the range went to zero, it took 11.3 gallons (going to 3 clicks, e.g. shutoff and 2 clicks more).

With a 12.7 gallon tank, that would leave 1.4 gallons. Maybe I didn't fill it. On the Miata forum, a guy claims you need to go to 5 clicks to fill the tank. Suspect that would take it to 1.3 gallons left like it says in the owners' manual (think that's what it says). NOT nearly 2 gallons as you guys are saying.

The Miata guy supplied this calibration for the NC Miata's fuel tank. It seems very similar to the way the 3's tank is.

Miata Fuel Gauge

Mark Liters Gallons Gallons
in Tank Down
5 clicks 48.0 12.7
F 40.1 10.6 2.1
38.3 10.1 2.6
37.6 9.9 2.8
3/4 36.7 9.7 3.0
33.1 8.8 3.9
28.2 7.5 5.2
1/2 24.9 6.6 6.1
21.1 5.6 7.1
17.7 4.7 8.0
1/4 13.8 3.6 9.0
10.9 2.9 9.8
8.2 2.2 10.5
light on 8.0 2.1 10.6
E 6.6 1.7 10.9

This calibration would support the 72 miles mentioned above. Maybe I was more below E when I filled up, for it to take 11.3 gallons.

In my very short experience with the Miata, the above actually seems to fit the 3 better than my Miata's. On my Miata, the gauge drops very quickly to around 3/4 tank within about 60-70 miles. It seems to be getting only about 23-25 mpg but ends up around 30 mpg when I fill it. Very limited experience so far though. Only one fillup so far and now down to about 3/4 again. (The 2006-2015 NC Miatas were not that great on fuel mileage.)

Ralph
 

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Crap, and I so carefully spaced out the info copied from Excel so the numbers would be in nice columns.'

On posting, it squashed it all in together.

Sorry, guys. I captured the Excel info in a png file and attached it to my above note.

Ralph
 

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When I refueled just after the range went to zero, it took 11.3 gallons (going to 3 clicks, e.g. shutoff and 2 clicks more). With a 12.7 gallon tank, that would leave 1.4 gallons. Maybe I didn't fill it. On the Miata forum, a guy claims you need to go to 5 clicks to fill the tank. Suspect that would take it to 1.3 gallons left like it says in the owners' manual (think that's what it says). NOT nearly 2 gallons as you guys are saying.
We've got 13.2 gallon tanks Ralph. So that seems consistent with what I've been getting seeing that you're also in VA with our recent chilly weather. 1.9 gallons left (not 1.4) is about right. You should notice closer to three gallons left once it warms up and we get better mpg's.

I never try to squeeze more gas in after the gas nozzle's auto-stop. So if that's what you mean by clicks, it's just one click for me. It clicks and I'm done. I use to top it off that way but then one of my former car's manual said not to. I also probably experienced some spillage once or twice so stopped the practice altogether.

I read where you got out the lawnmower to use its fuel after your new 3 hit 0. Just wanted to make sure to let you know that you shouldn't need to do that, ever again. :)
 

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Is our fuel tanks capacity actually 13.2 gallons or does that include the amount of fuel in the filler neck? Plus, the amount of fuel a vehicle will hold depends on which way the car is leaning while doing a fill up. Not all fuel station pumps are on level ground. If the car is leaning in the direction of the filler neck, then there could be air pockets trapped in the tank, reducing the capacity of the tank. Most of the time, I can get almost an entire gallon more fuel in 3MOE after the first auto-stop. With fuel still in 3MOE, I was able to put in 13.7 gallons once. I say there was still fuel in the tank, because I drove to the fuel station. I have gone over 600 miles on a tank of fuel in 3MOE.
 

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Here's my off-topic 2cents....Please don't run your tanks close to empty.....
To help extend our in-tank fuel pump life, avoid letting the car’s fuel level fall below the last quarter. The fuel is the pump's coolant. As the gas runs down to empty, the risk of overheating the pump goes up.
New petrol pumped into a suddenly empty tank may cause thermal shock to the pump.
Seen premature failure a few times.
 

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I had the same problem the first couple of months when filling up my tank, the expected range would always be 400-435 km more or less.

Then I realized that I was always filling my tank with 1/2 or 1/4 of gas in the tank and never when the range would reach 0 km. Therefore as an experiment I started filling my tank when the range would show 0 and drive on what "supposedly" is an empty tank for about 2-5km until re-fuel.

Now as an approximate, I know that in order to fill my tank as per my last 4 refuels I need 44 Liters of gas (51 Liters is the max, as per user manual, therefore 7 Liters are in reserve not calculated by the range algorithm) so after filling my tank from 0 km my range jumped from 435km to 640-680km!

So in brief, if you want to see your maximum range, wait until your range reaches 0, fill in the tank and see what is the new range number.

Real life example: After re-fueling I would see a range of 640km, do a trip of 150Km, and my range would show 670km afterwards (Driving not over 90km/hr). The algorithm analyzes the speed and distance you are traveling and what has been the consumption. Since every drive is a new drive the algorithm accommodates to that specific driving trip only and sets the range accordingly. From my experience after refueling if you drive properly and do not floor the gas, the range will increase, but if you floor the gas, the range will decrease rapidly!

I would also say as a humble guess, that the range stat is completely reseted when it reaches 0 and not while it still shows some range on the panel , therefore again as a humble guess IMO the range algorithm has already predetermined parameters which calculates the range when refilling completely the tank not taking into consideration your average mileage/ kilometers from previous drives.

To conclude, your range will depend mostly on your driving behavior / habits. The wiser you use the gas pedal, the better your range stats will be.

I hope this helps and that is was clear! :)

P.S: This is my own experience and this can vary from driver to driver.
 

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Great thread! I was just wondering about this information concerning when the fuel light would come on and if zero really meant zero. Good to know that it isn't necessarily so as I have a road trip coming up this summer that might warrant knowing what the tolerances are. As a rule, I never went below the 1/4 tank mark on my Element but it had a very long flat tank in which a steep mountain road could do you in. I'll have to look at the tank on the 3. Sounds like I can cruise quite a while longer below the 1/4 mark with the gas light being the time to look for a fill up but not necessarily be a NOW situation. (As in, gas light comes on, I have a few miles to find a station.)
 

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From my experience of filling up about 18 times to this point, range is calculated based on the full 13.2 gallons of fuel in tank. So unless you run until tank is completely dry, you'll never realize the range. My example, I get range of around 320 miles after fillup, but range shows 0 after only 240 miles. Filling up right when range shows 0, first click happens at about 10.2 gallons, so there's either 3 gallons left in the tank, pump is not calibrated or functioning correctly, or specified tank capacity is not what we think it is. It's annoying that actual usable fuel per fill is only about 10 gallons, and range estimate is misleading.
 

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Sounds like I can cruise quite a while longer below the 1/4 mark with the gas light being the time to look for a fill up but not necessarily be a NOW situation. (As in, gas light comes on, I have a few miles to find a station.)
My experience is that I have 20-30 miles left to go after the readout shows 0 miles left.
IOW, there's about a gallon still in the tank when the car wants you to get gas like "Right now!" As always, YMMW. :wink2:
 

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And a fun fact. Several members are balsy and hit the trip reset button when the Range hits 0 miles. They've confirm you can drive a good 40 - 50 miles before you actually run out of gas. I normally let my range hit 0 and then fill up. I don't take it much beyond that, but thanks to those members, I don't get nervous when I hit zero, I just know it's time to find a gas station.
Note the handbook states "The fuel gauge shows approximately how much fuel is remaining in the tank when the ignition is switched ON. We recommend keeping the tank over 1/4 full." Post 14 says this is to ensure the fuel pump stays cool and to avoid premature failure.
 

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So my fuel light went on when my range left meter read 35 miles left. I drove it until it was under 20 miles left before filling. I put in roughly 10.2 gallons which means there was still 3 gallons left. I was hitting roughly 31.5 mpg which would be about 90 miles left. Had 317 on the trip and when I started the tank out, it said I had a range of 405 miles to empty. It actually works out pretty neatly it seems at the start then the computer decides to start lopping miles off somewhere.

Looks like I need to get a couple more tanks like that in under my belt to get a better understanding of just how much is actually left.

This was all normal commuting. 25 miles each way with about 20 of it on interstates.
 
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