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nym85
04-05-2017, 09:37 PM
For starters, I'm completely new here and a completely new Fiat owner. I bought a used 2015 Fiat 500 sport with only a little over 23k miles on it back in February of this year. I'm a complete idiot when it comes to cars and I've been bugging the hell out of fiat studios and searching the internet like crazy for this "issue".
Basically, I filled up my tank on Sunday and it's now Wednesday and the gas gauge has only moved once. I drive pretty aggressively (I don't have a GoPedal yet from 500 Madness) and by now my tank usually moves about two or three spots. My anxiety compelled me to call the nearest Fiat studio and the guy was like "uh...just bring it in for us to check out."
Now I've been watching the fuel range and my average mpg and when I filled up my tank on Sunday the range read over 300 miles but steadily dropped down to the 290s. Today, on my way home from work, it's jumping from 230 to 234, to 224 and the avg mpg goes from 8.9 to 38 to 40s and when coasting to a complete stop it reads 99.9
IS THIS NORMAL and am I letting my anxiety get the best of me or could it be a bad sensor some place that needs to be replaced? Obviously, it's only Wednesday but I've never drove a car that had a practically full gas tank almost 4 days later.

PS.
I use only 91 octane.

Ducman69
04-05-2017, 10:17 PM
There's average fuel economy and instant fuel economy, and yes its normal for instant to go up and down as you are driving (as well the average if you reset the trip meter and it doesn't have enough miles to "smooth out" a average result). I would just do this. Fill up your gas tank tomorrow, reset your trip meter. Your range will be at least 200 miles, so just drive normally and after 200 miles check that you are at half a tank or so. Remember that on most cars when you fill up, you are filling up well past the full mark when you top off, so it can take a while even just to knock it down from full.

nym85
04-05-2017, 10:34 PM
if the tank doesn't go down to half by this coming Sunday should I worry and bring it in for a check up?
Thank you for your reply, by the way. I can't imagine this car having issues when it's barely 2 years old. Thankfully, it's still under warranty.

Fiat500USA
04-05-2017, 11:41 PM
Welcome to the forum. It is hard to judge anything without knowing how many miles did you drive since you filled up. Also, did you fill up with the car running or key on? When you fill up, do you stop filling as soon as the pump turns off or do you squeeze a little more in to top off or round off the money? Doing any of these things will likely cause an issue. Let us know.

Here is how the fuel gauge works among other things. http://www.fiat500usa.com/2013/02/a-look-at-fiat-500-instrument-panel.html

nym85
04-06-2017, 12:44 AM
Welcome to the forum. It is hard to judge anything without knowing how many miles did you drive since you filled up. Also, did you fill up with the car running or key on? When you fill up, do you stop filling as soon as the pump turns off or do you squeeze a little more in to top off or round off the money? Doing any of these things will likely cause an issue. Let us know.

Here is how the fuel gauge works among other things. http://www.fiat500usa.com/2013/02/a-look-at-fiat-500-instrument-panel.html

I have definitely driven less than 100 miles since filling up on Sunday. Work is about 10 miles each way with 90% city and the remaining on the freeway. I never fill up with the key in the ignition or with the car running because I've heard that can cause major issues for your car. I usually fill up until the pump turns off, never topping off to get that even round off.
I did, however, have my car towed to a Fiat studio last Thursday because the manufacturer battery went bad and they replaced it as well as reset the computer (all the service lights came on because of the bad battery).
i never let my tank get below a fourth of a tank either. Usually by Sunday it's just above a fourth so I fill up each Sunday for the work week. I noticed today that the car was running and picking up speed a lot better than it has, even with my aggressive, heavy foot.
No service lights are on, no funny smells or gasoline smells, the engine isn't running hot and the Fiat service studio did a check point inspection after replacing the battery.
Even with 91 octane, I haven't gotten THIS type of gas mileage...but I guess it would require me to watch it and see until Friday maybe? I've read on other non-Fiat forums that the gas gauge sendor could be stuck at full? When I got home, the ins. range was at 224 or 226 with the gauge still in the same place and the avg mpg jumping around from acceleration (8.09)and normal driving (38.9, 44.6, 36. Whatever) and coasting to a complete stop at a light (89 to 99.9)

Ducman69
04-06-2017, 02:24 PM
Average MPG should not be swinging that much after several miles. Sounds "jacked" (technical term, heh). I'd take note of that oddity, note the trip meter distance, and fuel after level after 200 miles or so and schedule a warranty drop-off. Hopefully they have a loaner for you.

MrFiat
04-06-2017, 08:16 PM
Generally speaking, you can expect 30 mpg on average with the Sport. That's a reasonably good benchmark. I notice on mine that the guage tends to stay high and starts dropping faster below half a tank.

********

This is not specific to your question, but a rather amusing related recollection from my far distant past. I think you might enjoy the story.

Back in the early 1960's when a VW Beetle was something of a rarity in the US, I was working at my first "real" job at a GM electrical parts manufacturing company in upstate NY. The marketing manager of the company had just purchased a new olive green VW Beetle and went around the factory bragging about his new car. As he had alway driven a US gas guzzler, the VW seemed to him to have unbelievable gas mileage. And he soon made a bit of a fool of himself bragging about how great the gas mileage on his new car was. (it was actually normal for the VW).

So we played along and several of us soon came up with a plan to deal with his constant bragging. Now, instead of draining gas from his tank as one might expect a prankster to do, we did the opposite. Every day we snuck into the parking lot and added a half gallon of gas or so to the Beetle. We never let the tank drop very much. Needless to say the man's mileage quickly began to climb. And the bragging got more and more ridiculous. He never suspected sabotage. After a couple of weeks things really became fun.

"Can you believe it?" he said "my car is getting over 400 miles to the gallon!" Yeah yeah sure it is, "it must be fitted with some new experimental carburetor or something". And the fuel was still added whenever the opportunity arose. Finally, after weeks of this when his mileage reached 900 miles per gallon or so we took the opportunity to drain his tank. Timing was perfect, The owner was taking the company president out to lunch in his miracle vehicle and when it reached the end of the parking lot it ran out of gas.

It took several weeks before someone in the know, leaked the truth. He took the news as graciously as anyone possibly could in that situation, but he never mentioned his VW after that.

nym85
04-06-2017, 09:59 PM
All in all, should I worry about the engine or fuel if I don't schedule it right this minute? I only ask because of my crazy work hours and the studios around here don't work on mechanical issues on the weekends, only maintenance like oil changes. The gauge did drop one bar this morning on my way to work which eased some of the anxiety and I reset the trip meter which gave me about 23.5 mpg. The ins range was at 219 but the avg mpg was still jumping around as I was driving. Basically, if this isn't an EMERGENCY issue that I could set aside a week or two then I hope that's fine...otherwise, I'll drop it off this weekend and have them check it during the week. What sucks is that the closest one is booked two weeks out and the one I went to for the battery change isn't as busy.

nym85
04-06-2017, 10:01 PM
Maybe there's a prankster like you where I work haha! jestera

pr0d1gy9
04-06-2017, 11:04 PM
Take a deep breath and gather your zen back, it doesn't sound like the car is having any problems to me. You should easily get 300 miles/tank unless you are constantly racing around in lower gears/higher rpms. You should be able to go at least two weeks without needing a fill up again unless you drive a lot on the weekends as well.

nym85
04-06-2017, 11:20 PM
Take a deep breath and gather your zen back, it doesn't sound like the car is having any problems to me. You should easily get 300 miles/tank unless you are constantly racing around in lower gears/higher rpms. You should be able to go at least two weeks without needing a fill up again unless you drive a lot on the weekends as well.

thank you
this is the first car I've bought on my own as an adult and it's given me SO much anxiety since purchasing it. And to think...I was going to put a Buddha decal on the back window :concern:

Fiat500USA
04-06-2017, 11:29 PM
For starters, I'm completely new here and a completely new Fiat owner. I bought a used 2015 Fiat 500 sport with only a little over 23k miles on it back in February of this year. I'm a complete idiot when it comes to cars and I've been bugging the hell out of fiat studios and searching the internet like crazy for this "issue".
Basically, I filled up my tank on Sunday and it's now Wednesday and the gas gauge has only moved once. I drive pretty aggressively (I don't have a GoPedal yet from 500 Madness) and by now my tank usually moves about two or three spots. My anxiety compelled me to call the nearest Fiat studio and the guy was like "uh...just bring it in for us to check out."
Now I've been watching the fuel range and my average mpg and when I filled up my tank on Sunday the range read over 300 miles but steadily dropped down to the 290s. Today, on my way home from work, it's jumping from 230 to 234, to 224 and the avg mpg goes from 8.9 to 38 to 40s and when coasting to a complete stop it reads 99.9
IS THIS NORMAL and am I letting my anxiety get the best of me or could it be a bad sensor some place that needs to be replaced? Obviously, it's only Wednesday but I've never drove a car that had a practically full gas tank almost 4 days later.

PS.
I use only 91 octane.


Is the Average MPG jumping around or is it the Instantaneous MPG? It is normal for the Instantaneous MPG to jump around like that. To find out, drive 200 miles, take a mental note or image of the fuel gauge and then fill up. If you take 5 gallons, then your gauge should have read about a 1/2 tank. Each of the 4 main segments on the gauge are about 2.5 -2.6 gallons so you can approximate what your gauge should have read before you filled up.

I think something like this was already posted, so pardon me for that, but in anycase, try it and let us know.

nym85
04-07-2017, 12:03 AM
Is the Average MPG jumping around or is it the Instantaneous MPG? It is normal for the Instantaneous MPG to jump around like that. To find out, drive 200 miles, take a mental note or image of the fuel gauge and then fill up. If you take 5 gallons, then your gauge should have read about a 1/2 tank. Each of the 4 main segments on the gauge are about 2.5 -2.6 gallons so you can approximate what your gauge should have read before you filled up.

I think something like this was already posted, so pardon me for that, but in anycase, try it and let us know.

Its definitely the average MPG. The instantaneous MPG jumps but not as much as the average.

Fiat500USA
04-07-2017, 09:54 AM
Its definitely the average MPG. The instantaneous MPG jumps but not as much as the average.

That is really weird and the opposite of normal. It should be the other way around. It is normal for the fuel range to change depending on the average mpg. I would try the 200 mile/fill-up idea to check the gauges accuracy. Let us know.

Shailer Andrew
04-07-2017, 02:45 PM
I'd like to see a video of you switching through the various readouts (Range, Avg, Inst... ETC) and arriving at which ones you think are average or instantaneous. The fact that what you are calling 'Average' is reading out exactly like the 'Instantaneous' makes me feel like you're incorrectly interpreting which readout you're on and that the car is operating normally.

Also, based on you stating that your fuel gauge has only gone down one bar (Assuming you reset the trip counter at fillup), it is not unreasonable to see large fluctuations in your Average MPG (Which you are calling Inst) because you have not driven many miles. If you drive 200 miles at 32 mpg and then one mile at 15 mpg it will have a lot less impact than 30 miles at 32 mpg and 1 mile at 15 mpg. This being said, I'm also pretty sure based on my observations that the range is estimated based on your Average MPG so both would be subject to change more drastically with less miles on the trip counter as you state. Regardless though, these fluctuations will not occur in sync with throttle position like the Instantaneous MPG (reading --- while coasting or 8 while full throttle).