Gas range dropping really fast! (2017 Civic)

JumBie

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First and foremost, I have only had this car for about 5 months and never got good "good" mileage out of it.

I filled up the tank this Saturday and my gas range read 415km 8.6L/100km (horrible mileage like I said). I took my car home parked it up at 410KM and left it all of Sunday. I hopped in the car this morning and the gas range was at 406...okay so that is weird. I drive to work, a smooth 3KM trip with the heat on low my gas range drops to 400, okay.. cool.

Get in my car today to go home and my range is at 394 (Dropped by 6km while parked). I have no heat on, I drive through the parking lot to get to the road, my gas range is now at 390, wow. I am in bumper to bumper traffic on a 3km trip with no heat on. I watch as my gas range drops by 1km every couple of minutes. I finally get home after 20 minutes and my gas range is now at 377.

So in the span of 20 minutes on a 3km trip my gas range dropped 17km. How is this even possible? From the time I filled my car up to the time I got home today I only drove 12 KM but my gas range dropped a total of 38KM. Should I be alarmed?



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fenix-silver

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From the owner's manual:
upload_2019-11-25_16-28-24.png

So, for instance, you fill up your car and then go for a highway drive. Your current fuel economy will be nice and high, so your estimate range will be high. Then you get into a city with tons of stop and go driving and your current fuel economy drops. Your estimated range will also drop quite substantially. (Note, I'm not actually positive what Honda mean's by "current fuel economy". Not sure if they mean instantaneous, in which case I'd think the range would be bouncing all over the place, or if it's some "recent" fuel economy calculation.)
 
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JumBie

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From the owner's manual:
upload_2019-11-25_16-28-24.png

So, for instance, you fill up your car and then go for a highway drive. Your current fuel economy will be nice and high, so your estimate range will be high. Then you get into a city with tons of stop and go driving and your current fuel economy drops. Your estimated range will also drop quite substantially. (Note, I'm not actually positive what Honda mean's by "current fuel economy". Not sure if they mean instantaneous, in which case I'd think the range would be bouncing all over the place, or if it's some "recent" fuel economy calculation.)
I understand that its showing a calculation based on previous calculations. However, I have never seen it drop this quickly. It was quite alarming and really didn't make any sense. I never drive on the highway, so really and truly my range should be the same all the time (even though its crap).
 

turbo lover

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Does it usually take you 20 minutes to drive 3km? I'm surprised that you're getting as good as 8.6L/100km with that kind of drive.
 

RufflesSCO

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Don't focus on the estimated range. If you're crawling in traffic, It's going to give you a range based off of that.

8.6 l/100km isn't bad either. The car is rated 7.8 city driving. I'm from Toronto too and the traffic is always horrible. Plus, we are currently running winter formulated gas which doesn't help our fuel economy. .
 

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IGNORE ESTIMATED RANGE, do actual calculations of fuel mileage, do NOT believe what the dash is telling you.
 

FC3L15B7

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First and foremost, I have only had this car for about 5 months and never got good "good" mileage out of it.

I filled up the tank this Saturday and my gas range read 415km 8.6L/100km (horrible mileage like I said). I took my car home parked it up at 410KM and left it all of Sunday. I hopped in the car this morning and the gas range was at 406...okay so that is weird. I drive to work, a smooth 3KM trip with the heat on low my gas range drops to 400, okay.. cool.

Get in my car today to go home and my range is at 394 (Dropped by 6km while parked). I have no heat on, I drive through the parking lot to get to the road, my gas range is now at 390, wow. I am in bumper to bumper traffic on a 3km trip with no heat on. I watch as my gas range drops by 1km every couple of minutes. I finally get home after 20 minutes and my gas range is now at 377.

So in the span of 20 minutes on a 3km trip my gas range dropped 17km. How is this even possible? From the time I filled my car up to the time I got home today I only drove 12 KM but my gas range dropped a total of 38KM. Should I be alarmed?
What I suggest is, fill it up and reset the mileage range if it's not programmed to reset automatically when you fill up; go for a drive on the highway with as little city driving as possible and drive at normal highway speeds. Look at what fuel mileage it's estimating over the course of several miles.

Naturally, you can't do this when traffic is heavy. It sounds to me like you're not going anywhere and it's idling or under load constantly, which would return a relatively low mileage, in addition to 3 km trips - the engine is still cold and never gets into the ultra fuel efficient range.
 

NotSerious

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The car's computer can't possibly figure out what your future mileage will be because it doesn't know whether it will be in stop and go or highway driving. It is just a very rough estimate. Ignore it.
 

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I don't see anything even remotely alarming in your range estimates and it makes perfect sense. Your trips after the fill up simply had worse mileage than what the computer had stored as then current average and so it started slightly correcting the predicted range down. 26 km correction from the the original range estimate is less than 10%. You can't possibly expect that the accuracy of the range estimate would be better than 10%. It's impossible, unless all your driving and the conditions are perfectly the same every trip.

But your mileage is indeed quite low. When I recently filled up, my range showed quite similar: 385. Miles. This converts to 620 clicks. And my gas mileage is not great either, because recently I have not done any longer trips. No Toronto here, but rush hour traffic, even on the freeway, does often stop almost completely.
 

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Something else to consider is Winter Gas. Fuel Companies change their mixture during the winter to help deal with the cooler temperatures. Here we are in late November, and I noticed that @JumBie is in Toronto. In general, summer gas has more energy in it than the winter counterpart. A few minutes on google for 'summer vs winter gas' should help. This is likely just one of the many factors that affect mileage. Speaking of, how is your tire pressure doing?
 
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JumBie

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What I suggest is, fill it up and reset the mileage range if it's not programmed to reset automatically when you fill up; go for a drive on the highway with as little city driving as possible and drive at normal highway speeds. Look at what fuel mileage it's estimating over the course of several miles.

Naturally, you can't do this when traffic is heavy. It sounds to me like you're not going anywhere and it's idling or under load constantly, which would return a relatively low mileage, in addition to 3 km trips - the engine is still cold and never gets into the ultra fuel efficient range.
I never get the chance to drive on the highway. In the morning its packed and when I get off work its packed. The only chance is on the weekend. I remember I took a long trip to London Ontario and came back. My mileage was still shit, even after filling up it read the same thing 8.6L. When I purchased the car, it was used and had 30000km on it, mileage was 7.0L/100KM and a full tank read over 500KM. It slowly went up over time. I don't drive aggressive, I rarely use the AC or Heat, so it just kind of sucks that my fuel economy is so low.

I don't see anything even remotely alarming in your range estimates and it makes perfect sense. Your trips after the fill up simply had worse mileage than what the computer had stored as then current average and so it started slightly correcting the predicted range down. 26 km correction from the the original range estimate is less than 10%. You can't possibly expect that the accuracy of the range estimate would be better than 10%. It's impossible, unless all your driving and the conditions are perfectly the same every trip.

But your mileage is indeed quite low. When I recently filled up, my range showed quite similar: 385. Miles. This converts to 620 clicks. And my gas mileage is not great either, because recently I have not done any longer trips. No Toronto here, but rush hour traffic, even on the freeway, does often stop almost completely.
I don't understand how people are getting that kind of mileage out of their tank.

Something else to consider is Winter Gas. Fuel Companies change their mixture during the winter to help deal with the cooler temperatures. Here we are in late November, and I noticed that @JumBie is in Toronto. In general, summer gas has more energy in it than the winter counterpart. A few minutes on google for 'summer vs winter gas' should help. This is likely just one of the many factors that affect mileage. Speaking of, how is your tire pressure doing?
I will definitely read into the winter vs summer gas. My tire pressure should be fine, I can double check. I just had brand new Michelin X-ICE 3's put on.
 

turbo lover

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I don't understand how people are getting that kind of mileage out of their tank.
It's easy to get 600km/tank, it's just steady speed highway driving without many slowdowns from traffic.
 

FC3L15B7

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I never get the chance to drive on the highway. In the morning its packed and when I get off work its packed. The only chance is on the weekend. I remember I took a long trip to London Ontario and came back. My mileage was still shit, even after filling up it read the same thing 8.6L. When I purchased the car, it was used and had 30000km on it, mileage was 7.0L/100KM and a full tank read over 500KM. It slowly went up over time. I don't drive aggressive, I rarely use the AC or Heat, so it just kind of sucks that my fuel economy is so low.
Wait, wait, wait.. Please tell me you are either manually resetting and reading Trip metre A or its set up to reset Trip A automatically when you refuel?

If you're filling up and it's not resetting back to 0 L/100 KMS, it's not set up to reset at fillup. If you average 8.6L over the course of say, 10,000kms and never reset the metre, then expect it to fall under 8.6L all of a sudden, it's not going to happen. Reset the Trip meter A, or use automated reset functions as described in the video I've posted for you.

 
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Beansley

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Something else to consider is Winter Gas. Fuel Companies change their mixture during the winter to help deal with the cooler temperatures. Here we are in late November, and I noticed that @JumBie is in Toronto. In general, summer gas has more energy in it than the winter counterpart. A few minutes on google for 'summer vs winter gas' should help. This is likely just one of the many factors that affect mileage. Speaking of, how is your tire pressure doing?
yup, this right here, i have noticed that my average MPG has dropped prob about 0.5 MPG and i know a factor is winter blend gas, not only that but colder temperatures i believe can make it even as low as 20% lower MPG.
 

FC3L15B7

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yup, this right here, i have noticed that my average MPG has dropped prob about 0.5 MPG and i know a factor is winter blend gas, not only that but colder temperatures i believe can make it even as low as 20% lower MPG.
If you used summer gas blends in the winter, you'd have a lot of unburned fuel, rough starts, rough drive and misfiring until it gets hot, higher NOx and damaged catalytic converters. Whatever you lose with higher volatility gas in the winter, you'd get back in the long run in all likelihood. I honestly wouldn't worry about it. Winter is a survival game in all aspects. :)
 

                           

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