Gas Mileage

LeaveEarly

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This was from driving 5
105 km/hr without eco

20170706_111430.jpg



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bubbaleenc

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This was from driving 5
105 km/hr without eco

20170706_111430.jpg
The 4 l/100km (58mpg US) is sweet... but that 10.6 (22mpg US) is ugly! Must have been having fun on that trip!!! :) :) :)
 

LeaveEarly

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The 4 l/100km (58mpg US) is sweet... but that 10.6 (22mpg US) is ugly! Must have been having fun on that trip!!! :) :) :)
Yeah the acc and Lkas make cruising at 105 km/hr a blast. The previous trip was 1km driving and 80% was idling at a drive thru
 

bubbaleenc

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Yeah the acc and Lkas make cruising at 105 km/hr a blast. The previous trip was 1km driving and 80% was idling at a drive thru
Well that isn't ugly at all then!
 

hunterbott

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The first time I filled up my new Civic the dashboard display's average said 33.1mpg but if I divided the mileage by the amount I pumped it was 32.6-something. So I guess in round numbers I'm getting 33mpg. That's about 1/3 Interstate and 2/3 mixed city and secondary road in a 2.0/CVT sedan.

That seems to be somewhere right around 30mpg in town and a bit over 40mpg on the highway so pretty close to the EPA numbers. I've always found my cars to get somewhere in the vicinity of their EPA ratings.

BTW, I do keep the "Eco" mode on when I'm driving.
Next tank full the "Average Fuel Economy Trip A" said 34.3 but the miles divided by gallons gave 33.45mpg. So this time almost a full MPG overstatement from the dashboard display.

Overall it looks like my dashboard display is going to tell me I'm getting maybe 3/4 of a mile per gallon better than I am. That's tolerable accuracy I guess.
 

shire123

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Next tank full the "Average Fuel Economy Trip A" said 34.3 but the miles divided by gallons gave 33.45mpg. So this time almost a full MPG overstatement from the dashboard display.

Overall it looks like my dashboard display is going to tell me I'm getting maybe 3/4 of a mile per gallon better than I am. That's tolerable accuracy I guess.
After 5 months of keeping records of the dashboard display and actual calculated it turned out to almost exact on average. The range was from 1mpg over dashboard to 1mpg under dashboard with about an equal number over and under.
I stopped keeping records and now just spot check and it still is the same. My previous car was always about 2mph over on the dashboard.
 

bubbaleenc

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I originally thought mine dash computation was consistently about 3% above hand calculation. I was going to the same gas station that had only 2 pumps and filling by coincidence at the same pump each time. Then on my first trip I noticed my dash computation had a different offset from hand calculations - I just figured the computer handled the computations differently or something without a whole lot of thought. Then I changed jobs and began going to another gas station regularly. I noticed when I used one pump, the dash was consistently within 0.3mpg - but using another my dash was consistently overstating by about 1.5%.

So here's the issue: if a gas pump is not metering correctly and is only pumping 0.97 gallons per 1.0 gallon metered, the hand calculation will be off accordingly. Say you drive exactly 100.0 miles and the dash says you got 40.0mpg, the dash states you used 2.5 gallons of gas. But at this pump example, the pump says you pumped 2.575 gallons (since it is under pumping / over charging by 3%) therefore netting 38.8mpg.

In NC the Department of Agriculture "certifies" pumps every couple of years, but with all the pumps in the state I know the quality of certification is pretty poor. One example was when I drove my 4Runner to a pump that said it added more fuel than my tank will hold - and the gas light wasn't even on yet (comes on at 1 gallon remaining). That was an extreme example of at least 10% under pumping, but I wonder if I wouldn't have noticed it on a smaller gas tank.

In short, I am now hesitant to believe pump calcs over dash calcs since 95% or more of the reported mpg differences are in the gas station's favor. The fuel metering in cars now is exceptionally precise - especially in our Direct Injection engines (It has to be to work correctly). Odometers are incredibly precise when the car is fitted with properly matched tires and wheels (Even worn tires with a smaller diameter will only give more revolutions per mile by a fraction of 1%).

Side note: I'm not accusing anyone of fraud, especially small business owners who run most gas stations. I am saying that calibrations that are "good enough" to be legal at time of certification are almost certainly not 100% perfect, so why not err on the side of the gas supplier? Each driver's fill up will only be overcharged by a few cents to maybe a dollar - not enough to cause anyone to complain when they are paying over $20 a tank for gas in the first place. The aggregate to the gas station will be several hundred dollars a month, but still only a very small fraction of overall revenue (and certainly not enough to raise red flags with authorities. Besides, authorities would only impose relatively modest fines even if a business was caught intentionally under pumping - the bad PR would cost more than the fine).
 

shire123

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I originally thought mine dash computation was consistently about 3% above hand calculation. I was going to the same gas station that had only 2 pumps and filling by coincidence at the same pump each time. Then on my first trip I noticed my dash computation had a different offset from hand calculations - I just figured the computer handled the computations differently or something without a whole lot of thought. Then I changed jobs and began going to another gas station regularly. I noticed when I used one pump, the dash was consistently within 0.3mpg - but using another my dash was consistently overstating by about 1.5%.

So here's the issue: if a gas pump is not metering correctly and is only pumping 0.97 gallons per 1.0 gallon metered, the hand calculation will be off accordingly. Say you drive exactly 100.0 miles and the dash says you got 40.0mpg, the dash states you used 2.5 gallons of gas. But at this pump example, the pump says you pumped 2.575 gallons (since it is under pumping / over charging by 3%) therefore netting 38.8mpg.

In NC the Department of Agriculture "certifies" pumps every couple of years, but with all the pumps in the state I know the quality of certification is pretty poor. One example was when I drove my 4Runner to a pump that said it added more fuel than my tank will hold - and the gas light wasn't even on yet (comes on at 1 gallon remaining). That was an extreme example of at least 10% under pumping, but I wonder if I wouldn't have noticed it on a smaller gas tank.

In short, I am now hesitant to believe pump calcs over dash calcs since 95% or more of the reported mpg differences are in the gas station's favor. The fuel metering in cars now is exceptionally precise - especially in our Direct Injection engines (It has to be to work correctly). Odometers are incredibly precise when the car is fitted with properly matched tires and wheels (Even worn tires with a smaller diameter will only give more revolutions per mile by a fraction of 1%).

Side note: I'm not accusing anyone of fraud, especially small business owners who run most gas stations. I am saying that calibrations that are "good enough" to be legal at time of certification are almost certainly not 100% perfect, so why not err on the side of the gas supplier? Each driver's fill up will only be overcharged by a few cents to maybe a dollar - not enough to cause anyone to complain when they are paying over $20 a tank for gas in the first place. The aggregate to the gas station will be several hundred dollars a month, but still only a very small fraction of overall revenue (and certainly not enough to raise red flags with authorities. Besides, authorities would only impose relatively modest fines even if a business was caught intentionally under pumping - the bad PR would cost more than the fine).
Good point! Had the same thing happen to me a number of years ago, were the pump "allowed" me to put in more gas than the tank would hold!
 

oshoguno

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I originally thought mine dash computation was consistently about 3% above hand calculation. I was going to the same gas station that had only 2 pumps and filling by coincidence at the same pump each time. Then on my first trip I noticed my dash computation had a different offset from hand calculations - I just figured the computer handled the computations differently or something without a whole lot of thought. Then I changed jobs and began going to another gas station regularly. I noticed when I used one pump, the dash was consistently within 0.3mpg - but using another my dash was consistently overstating by about 1.5%.

So here's the issue: if a gas pump is not metering correctly and is only pumping 0.97 gallons per 1.0 gallon metered, the hand calculation will be off accordingly. Say you drive exactly 100.0 miles and the dash says you got 40.0mpg, the dash states you used 2.5 gallons of gas. But at this pump example, the pump says you pumped 2.575 gallons (since it is under pumping / over charging by 3%) therefore netting 38.8mpg.

In NC the Department of Agriculture "certifies" pumps every couple of years, but with all the pumps in the state I know the quality of certification is pretty poor. One example was when I drove my 4Runner to a pump that said it added more fuel than my tank will hold - and the gas light wasn't even on yet (comes on at 1 gallon remaining). That was an extreme example of at least 10% under pumping, but I wonder if I wouldn't have noticed it on a smaller gas tank.

In short, I am now hesitant to believe pump calcs over dash calcs since 95% or more of the reported mpg differences are in the gas station's favor. The fuel metering in cars now is exceptionally precise - especially in our Direct Injection engines (It has to be to work correctly). Odometof mile by a fraction of 1%).

Side note: I'm not accusing anyone of fraud, especially small business owners who run most gas stations. I am saying that calibrations that are "good enough" to be legal at time of certification are almost certainly not 100% perfect, so why not err on the side of the gas supplier? Each driver's fill up will only be overcharged by a few cents to maybe a dollar - not enough to cause anyone to complain when they are paying over $20 a tank for gas in the first place. The aggregate to the gas station will be several hundred dollars a month, but still only a very small fraction of overall revenue (and certainly not enough to raise red flags with authorities. Besides, authorities would only impose relatively modest fines even if a business was caught intentionally under pumping - the bad PR would cost more than the fine).
A very good point. I don't think it is as bad as all that myself. Mechanical/electrical systems like you see on pumps are much more reliable than years ago. Are they perfect? Obviously not and there may be some discrepancy, but I used brand new gas station for a while on my last car and it didn't change the discrepancy between my dash and calculated readings at all. I still believe it is a bias built into the cars cpu. My discrepancy has improved since the break-in period. It was was off by 2.5L/100km (1.57mpg) for the first 7500km and since has been off by 1.2L/100km (0.74mpg) for the next 5000+km. I haven't changed the stations I visit, the route I take or my driving style.

upload_2017-7-14_14-17-19.png
 
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Mattman1206

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My 2016 Honda Civic Touring Coupe was getting around 28mpg in town. Recently, it's only been getting about 18mpg. I have noticed what I thin is a slight miss. Any ideas?
 

gtman

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My 2016 Honda Civic Touring Coupe was getting around 28mpg in town. Recently, it's only been getting about 18mpg. I have noticed what I thin is a slight miss. Any ideas?
Do you happened to live in a cold weather State? In Maryland this winter my MPG's have dropped around 25% in temps below freezing.
 

SI_honda_2k17

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I'm quite impressed, for my 3 first tank on my civic SI, I calculated 38.6, 36.1 and 35 mpg. I driving on winter tires at temperature around -10 to -15 degree C. Way better than my 9th gen which average 30-31 mpg in the same condition.
 
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