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Isaac
10-16-2015, 05:38 PM
Here's a question for other mileage freaks (like me):

I've been checking my manual 500's instantaneous economy on the dashboard in order to improve the car's mileage. I've noticed that while going downhill and putting the gearbox in neutral (in order to improve mileage), the instantaneous economy stops recording the mileage and only shows two lines. If those lines mean zero (and that zero is pulling down the average economy), does it mean that by going downhill on neutral, I'm making my mileage readings worse???

I know I may sound cheap, but going downhill without accelerating is a trick that has served me well over the years!

SweetSandMan
10-16-2015, 05:52 PM
That happens any time it estimates greater than 99 mpg. Does it in the Abarth too. In fact, that happens in a lot of cars. My wife's Cruze does that. My old Mazdaspeed3 did that, my old WRX did that, my old Cobalt SS did that. Not sure what the reason is, though.

Andree
10-16-2015, 05:52 PM
There are two reasons to get --.--

--.-- may stand for zero miles per gallon, such as idling. In my opinion, it would have really gotten people's attention more if it did indeed say 00.00

--.-- also shows outside of range, beyond 99.99 miles per gallon. This result is when you are coasting, usually on a down slope of any kind. This equates to Infinity*.

*Disclaimer, obviously you will run out of gas eventually if the engine is on, as you could idle away the entire tank of gas at a standstill

The lower the idle, the better the mpg when cruising along, which is why the 6 gear automatic easily does as well as the 5 gear manual. The 6th gear being the overdrive, with the lowest idle.

If you're gliding, it's adding in, 99.99 mpg or 100 mpg, not the zero.

They have to draw the line somewhere, and 99.99 is a good one. I don't know if there is a road anywhere that is long enough to fully test this out, you'd need 99 miles downhill. You'd need to see if you do indeed use a gallon of gas while coasting downhill for 99 miles.

Maricopaman
10-16-2015, 05:56 PM
I'm not sure how their system works, but I've noticed some strange readings on my automatic as well. Many times when I come to a complete stop the instant mileage will actually go up for half a minute and no throttle down hills the mileage will drop. After refueling and resetting the average will do the same kind of weirdness but levels off as the miles increase. I know some people get crazy about this kind of thing, to me, it's just a distraction and I concentrate more on the joy of driving the car.

Maricopaman
10-16-2015, 06:02 PM
There are two reasons to get --.--

--.-- may stand for zero miles per gallon, such as idling. In my opinion, it would have really gotten people's attention more if it did indeed say 00.00

--.-- also shows outside of range, beyond 99.99 miles per gallon. This result is when you are coasting, usually on a down slope of any kind. This equates to Infinity*.

*Disclaimer, obviously you will run out of gas eventually if the engine is on, as you could idle away the entire tank of gas at a standstill

The lower the idle, the better the mpg when cruising along, which is why the 6 gear automatic easily does as well as the 5 gear manual. The 6th gear being the overdrive, with the lowest idle.

If you're gliding, it's adding in, 99.99 mpg or 100 mpg, not the zero.

They have to draw the line somewhere, and 99.99 is a good one. I don't know if there is a road anywhere that is long enough to fully test this out, you'd need 99 miles downhill. You'd need to see if you do indeed use a gallon of gas while coasting downhill for 99 miles.
Actually the automatic doesn't come close to the manual in MPG, the manual Abarths get better mileage than my auto Sport. Up until this week I was averaging around 28-29 in mixed driving, mostly rural, this week it bumped up to 32 because I was doing jury duty 59 miles away and was driving on 55 MPH roads which bumped it up over the normal 65 MPH in the area I live. Actually, because my foot is on the floor board a lot of the time my mileage cannot be considered typical. ;>)

tknospdr
10-17-2015, 08:48 AM
Since I've been using non-ethanol 93 octane gas and no AC, I've been getting 34 to 36 mpg on every tank. And I still drive it like I stole it.

Andree
10-17-2015, 11:38 AM
Actually the automatic doesn't come close to the manual in MPG, the manual Abarths get better mileage than my auto Sport. Up until this week I was averaging around 28-29 in mixed driving, mostly rural, this week it bumped up to 32 because I was doing jury duty 59 miles away and was driving on 55 MPH roads which bumped it up over the normal 65 MPH in the area I live. Actually, because my foot is on the floor board a lot of the time my mileage cannot be considered typical. ;>)

All I can tell you is that I am absolutely thrilled with the mpg in my new Arizona area. My last little trip gave me the 40 mpg highway, and I've left the trip odometer on after that. With my around town driving HERE (Remember: It's not the car, it's where you are), my overall average is 32. Here, only.

Here's the automatic, stick, turbo, Abarth, from 2013:
http://fueleconomy.gov/feg/Find.do?action=sbs&id=33029&id=33030&id=33027&id=33028

What I'm getting in my current location is what the EPA estimates for the stick. I'm not running Premium these days, running Regular. I don't know about Ethanol, but I noticed some pumps say they may contain Ethanol. I don't know if that's good or bad for mpg. So I looked it up...and found an interesting tidbit:

"The first production car running entirely on ethanol was the Fiat 147, introduced in 1978 in Brazil by Fiat"
https://en.wikipedia.org/wiki/Ethanol_fuel

I couldn't be more pleased with my fuel economy now that I'm in a location that maxes out mpg.

rustbucket
10-17-2015, 11:57 AM
Since I've been using non-ethanol 93 octane gas and no AC, I've been getting 34 to 36 mpg on every tank. And I still drive it like I stole it.

The BP stations in my neck of the woods have switched their premium (aka Amoco Ultimate) to 91 octane ethanol free and by my reckoning it's worth 1 to 2 mpg ... been averaging 37 to 38 mpg and that's with the Sport button on 99% of the time. Motor starts easier (fewer revs before it fires), is more eager to rev and the seat of the pants dyno says it makes more power. Good stuff.

Haven't done the calcs yet but from a financial standpoint I seriously doubt the extra mpg is enough to offset the additional cost vs. the 87 and 89 octane E10 fuels but for me, the improvements are well worth the cost.

Maricopaman
10-18-2015, 12:19 PM
Andree, you would probably have been even more thrilled in pre-stoplight Cottonwood, it has grown significantly over the past 20 years. As with the area I'm in population has exploded (we had 0 stoplights and 1,100 population, now we have 12 stoplights and 47,000) Does your L have a regular automatic? Not real familiar with that version. I noticed on my drive last week how small towns gouge citizens on gas. In Maricopa it is $2.09, Casa Grande it is $2.03, Coolidge and Florence $2.45! Ouch!
I use premium exclusively, it may cost .30 more a gallon but the engine was designed for premium, the computer has to de-tune the engine to make it run on regular, I say if the child wants ice cream give it ice cream! I think all of Arizona has ethanol or methanol in it's gas most of the year due to climate. Speaking of climate, I'm sure my mileage will jump dramatically in a month when I finally get to turn off the A/C, it always made a big difference in my Focus and Fiesta!

Andree
10-18-2015, 12:51 PM
Andree, you would probably have been even more thrilled in pre-stoplight Cottonwood, it has grown significantly over the past 20 years. As with the area I'm in population has exploded (we had 0 stoplights and 1,100 population, now we have 12 stoplights and 47,000) Does your L have a regular automatic? Not real familiar with that version. I noticed on my drive last week how small towns gouge citizens on gas. In Maricopa it is $2.09, Casa Grande it is $2.03, Coolidge and Florence $2.45! Ouch!
I use premium exclusively, it may cost .30 more a gallon but the engine was designed for premium, the computer has to de-tune the engine to make it run on regular, I say if the child wants ice cream give it ice cream! I think all of Arizona has ethanol or methanol in it's gas most of the year due to climate. Speaking of climate, I'm sure my mileage will jump dramatically in a month when I finally get to turn off the A/C, it always made a big difference in my Focus and Fiesta!

I have the regular 500, not the 500L, and it's the "regular" automatic, not the heavy duty Abarth style. I believe it is the same automatic that you have in your Sport. I just don't have the Sport-tuned suspension.

Our gas here is in between the costs you mentioned, looks like $2.35 according to Gas Buddy for regular. Don't think I've seen prices as low as what you mention, not since I've been here.

I don't drive all that much, although I've been trying to explore a little more around town. Trying to familiarize myself with all the main roads and check out little shops along the way. I'd like to eventually eat at all food places and visit all businesses. It would be especially nice to buy from each business. Good for the local economy. If everyone made that kind of effort, all the little shops would be better off, with a steady flow of customers checking everything out, buying something as needed, or grabbing a snack/having a meal. If we want to keep our home areas thriving, it's up to us to be part of the solution by trying them all out. It's how to keep the storefronts occupied.

It doesn't have to be a big purchase either, if everyone does it. With your 47,000 people, if everyone hits a donut shop and buys one donut at 75 cents or so, $35,250 dollars worth of donut sales will be made! Spreading out one's wealth to the community keeps it going. Even if it's just 75 cents.

I'm getting such good mpg now, on regular, using a/c, that I'm not sure what I'll do if it gets better. haha. And the prices for gas here are about a dollar less than San Francisco. Things are just going too good. The wide open spaces, the scenery, the gas mpg, the costs of gas, I'm pretty sure this must be paradise.

Except for the neighbors who do not pick up their leaves, leaving the leaves to blow over onto my yard making it harder for me. Grrr. On the other hand, I HAVE a yard, so that's a bright spot in every day and I get a little exercise walking around, doing my own leaves.

Maricopaman
10-18-2015, 01:26 PM
Hah, hah, well, I don't know where I got the idea you had an "L". The highest MPG I've seen was 40.3 downhill to Casa Grande (not a hill, just slope) with the A/C off in the morning. I do know that I would get better mileage if I didn't almost always press the peddle all the way to the floor on acceleration and hold the shifts to redline (I only use auto on road trips). The road to Casa Grande (18 miles) is 55MPH, the 4 lane to Maricopa (15 miles) is 65MPH. I plead the 5th as to whether I drive the speed limit or not!

dart1.4t
10-18-2015, 01:43 PM
its more likely to mean infinity or more literally an undefined number as it is a number divided by zero which isn't explicitly infinity but in this case it is sorta the same. the car will go into fuel cutoff mode in decel conditions at anything over 1500 rpm. i dont have a 500 so i dont know how it behaves but if you hit the clutch preventing fuel cutoff mode at a speed high enough for idle to still work out to over 99 mpg and it swaps out the 2 lines for the number 99 then it indicates fuel cutoff mode and an undefined value. if it still reads the 2 lines then it just means it exceed 99. my dart just tops out at 99 and doesn't indicate whether it is higher nor does it indicate fuel shutoff it handles the display differently than the fiat. how it play into the average i don't know. the fiat and the dart might not even be the same. i notice a bit of smoothing in my instantaneous gauge. maybe over 3 seconds or so. but how it plays into the average gauge is not clear. after about 500 miles the rate that the current state of driving alters the average seems to level off. there must be a limit to the data points it can record and calculate with. but there can be a few methods and whether it is recording those undefined data points or recording them as a manageable defined value may have a negative effect on the readout as anything compared to infinity is less but they might use values high enough for this to matter to a negligible amount or build in some optimism to the measurements to counter the effects or have multiple layers of averaging or some clever way to do it i haven't thought of.

either way the gauge can only be so accurate and it seems to self calibrate over time. it may be more accurate with different driving styles. another thing is the instant gauge isn't always the best way to watch your mileage. understanding the physics and the engine are also important. for one thing fuel mass burned has more to do with speed than distance or g force of acceleration. more speed is more friction to the air and more speed means more energy in the car the amount of energy it took to get that energy in the car varies very little and is based on efficiency. the goal is not to keep the engine sipping gas all the time, it's to get the energy into the car with as little fuel as possible and to also coast as much as possible and use as little speed as possible. some of these things are contradictory. i mean coasting with the engine idling give more mileage while coasting faster than slower for instance unless you want to shut the engine off in which case speed doesn't matter, and engines make more power per fuel used when they are at torque peak. but being at torque peak rpm and not using all the torque doesn't work either. you want to use all the engines torque but only the power you need which means lower rpms and higher gears, the cylinder pressure and engine torque will come naturally with that condition. but that's not always possible. that all said the fiat's engine is pretty good at keeping things efficient no matter how you drive it. the body is not that areo. my point is really that you shouldn't worry so much about avoiding a dip in the instant gauge at all because using marginal power might keep you from coasting longer. you should instead worry about speed and coast down distance. if you are going stop sign to stop sign you might only want to get up to 10mph and put the car in neutral. anticipate your stops and coast down. if you can anticipate your stops to let the car coast to 10-15 mph before you hit the brakes a short distance away you will do good with mileage, if you need to stop in a shorter distance than that leave it in a low gear and decel to a stop to activate the fuel cutoff mode.

because the engine is more efficient under high torque conditions aggressive starts aren't all that bad especially if you short shift it, however that's efficiency but mpg is not efficiency because distance is not a factor of energy like speed and height are. this is how things get weird, slower acceleration takes more distance to get to speed. the energy is the same, the efficiency is lower, but so perhaps a little more fuel per mph is used but the distance is greater before that amount of energy enters the car and the distance is greater before you pile up all the wind resistance subtracting from your energy so the mileage may be somewhat higher depending on the car despite lower efficiency in the powertrain... as you can see its complicated on the acceleration end of things but speed and anticipation will help you manage fuel consumption in any situation. coasting is better than decel despite fuel shutoff because turning the crank slower is better than turning it faster and it will prolong the distance the car travels for it's speed. but if brakes and decel are needed then use fuel cutoff mode all you can.

piotrush
11-11-2016, 11:38 AM
My impression is that while you are coasting in neutral, you're consuming as much fuel as you would at idle. While you're coming to a stop in any gear (engine breaking) the injectors do not fire, therefore the car uses zero fuel. It is much easier to hear the injectors on my TDi than the Abarth, but I think the same applies to both diesel and gas cars. Correct me if I'm wrong.

KellyfromVA
11-15-2016, 12:23 PM
If your fuel injectors didn't operate ("fire") while coming to a stop, it would be like shutting off the fuel supply and the engine wouldn't be running at all. Taking your foot off the accelerator just means the fuel delivery goes to just above idle, depending on RPM and the the air moving through the MAF sensor.

piotrush
11-15-2016, 05:55 PM
I'm pretty sure with in an electronic flue injected car, that is exactly what happens; fuel is cut off from the car. The engine makes no power in that circumstance and therefore uses no fuel. The only thing keeping it "running" is the inertia of the car moving forward while in gear.

Doohickie
11-15-2016, 06:56 PM
...and I'm pretty sure you're wrong. Next time you're coasting downhill on a straightaway, shut your engine off. You'll be able to hear the difference.

fierostetz
11-15-2016, 07:14 PM
I'm not sure how their system works, but I've noticed some strange readings on my automatic as well. Many times when I come to a complete stop the instant mileage will actually go up for half a minute and no throttle down hills the mileage will drop. After refueling and resetting the average will do the same kind of weirdness but levels off as the miles increase. I know some people get crazy about this kind of thing, to me, it's just a distraction and I concentrate more on the joy of driving the car.

well, if you focus on NOT enjoying the drive, you'll get better mileage :)

fierostetz
11-15-2016, 07:16 PM
Combustion is still occurring so it's still eating fuel - however, it's below the threshold for the computer's ability to meter it, or the computer's ability to display it. It's just "out of range". I had a VW that didn't have a metered cutoff, before an ECU reflash it'd display "430mpg" on a long downhill. After a reflash it would display 0 any time the number was over 99. It's normal.

KellyfromVA
11-15-2016, 07:31 PM
Combustion is still occurring so it's still eating fuel - however, it's below the threshold for the computer's ability to meter it, or the computer's ability to display it. It's just "out of range".

Combustion requires fuel, air and spark. Take any of the three away, no combustion. As Doohickie says, it would be the same and turning off the key going downhill, which in normal operation isn't what happens when you go downhill with your foot off the accelerator. The fuel injection, based on the throttle position encoder, goes to idle fuel delivery.

One of the other replies was correct when they said the estimated instant MPG exceeds the amount of range the display can indicate with the engine at idle, yet the wheel speed sensors indicating forward motion. Has nothing to do with the fuel injectors not-firing, because they are as long as the car is running.

piotrush
11-16-2016, 02:37 PM
Combustion requires fuel, air and spark. Take any of the three away, no combustion. As Doohickie says, it would be the same and turning off the key going downhill, which in normal operation isn't what happens when you go downhill with your foot off the accelerator. The fuel injection, based on the throttle position encoder, goes to idle fuel delivery.

One of the other replies was correct when they said the estimated instant MPG exceeds the amount of range the display can indicate with the engine at idle, yet the wheel speed sensors indicating forward motion. Has nothing to do with the fuel injectors not-firing, because they are as long as the car is running.

Must be a diesel thing for me then; when I'm engine braking in the TDI, I can actually hear the injectors kick in as the rpm needle approaches idle. Thanks for clarifying!