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Old 08-31-2018, 05:46 PM   #1 (permalink)
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Unhappy MPG - Actual vs Insight gauges

I have had my Insight EX for two weeks and it now has 658 Smiles.

The gauges in the car indicate that I have been averaging 51.9 mpg, However when I fill the car up at the gas station ( twice) my Actual MPG is more like 47 mpg. That is close to an 8% error.


47 mpg is good but my expectations were effected by the Insight's gauges, and therefore I'm disappointed.
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Old 08-31-2018, 06:46 PM   #2 (permalink)
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My indicated has always been UNDER the actual over the past few tanks by a couple mpg. I've been around 59.7 indicated, 61.1 actual. Indicated is an approximation. Only hard numbers will be accurate. Since you're in the high 40's, I need to ask - what mode to you drive in primarily (eco, normal, sport), and are you a "spirited" driver? You should be at least in the low 50s unless your trips are very short.
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Old 08-31-2018, 09:26 PM   #3 (permalink)
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My indicated has always been UNDER the actual over the past few tanks by a couple mpg. I've been around 59.7 indicated, 61.1 actual. Indicated is an approximation. Only hard numbers will be accurate. Since you're in the high 40's, I need to ask - what mode to you drive in primarily (eco, normal, sport), and are you a "spirited" driver? You should be at least in the low 50s unless your trips are very short.
I have always used ECO mode and since I'm 71, I drive slowly because I have no need to rush around. I also use the paddle regenerative pads when approaching a stop. I cruse to stops, and start slowly.

Like I said the Insight indicates an Average of 51.9 mpg. The car has indicated over 70 mpg on some trips, but I do take a lot of short trips (City Driving), so I should be getting much better gas mileage.

47 mpg Actual vs 52 mpg indicated is a Big discrepancy
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Old 08-31-2018, 10:00 PM   #4 (permalink)
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I have always used ECO mode and since I'm 71, I drive slowly because I have no need to rush around. I also use the paddle regenerative pads when approaching a stop. I cruse to stops, and start slowly.

Like I said the Insight indicates an Average of 51.9 mpg. The car has indicated over 70 mpg on some trips, but I do take a lot of short trips (City Driving), so I should be getting much better gas mileage.

47 mpg Actual vs 52 mpg indicated is a Big discrepancy
City driving is all well and good, but if the trips are short, the engine will not go into EV move during ECO unless it is up to operating temperature. I feather throttle when I drive to try to force EV mode as much as possible. The increased regen via paddle shifter is best used on a loooong downhill. Short uses haven't proved to be that beneficial. Also, staying below the "hump" in the accelerator pedal will save tons. If you floor it, you're wasting gas. The best advice I can give it to get up to speed slowly, and stay out of the "power" section of the gauge as much as possible. Just those two things have proved successful to the point of 60+ mpg.
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Old 09-02-2018, 06:53 PM   #5 (permalink)
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Originally Posted by dave92029 View Post
I have had my Insight EX for two weeks and it now has 658 Smiles.

The gauges in the car indicate that I have been averaging 51.9 mpg, However when I fill the car up at the gas station ( twice) my Actual MPG is more like 47 mpg. That is close to an 8% error.


47 mpg is good but my expectations were effected by the Insight's gauges, and therefore I'm disappointed.
Dave, two factors come to mind to possibly explain that 8% error. (1) Gas tank not being filled to the same point each time. (2) Tire pressures too low.

Regarding (1): To accurately determine the amount of gasoline used, the tank has to be filled to EXACTLY the same point as the prior fillip. The automatic turn off is not accurate enough for this calculation. The nozzle can be ajar in one way or another on one fill up, but not on the other. If the nozzle is inserted exactly the same both times, any kind of additional gas beyond the auto turn off, to will give ya that kind of error.

The source of the error has to do with the determination of the amount of gas used; that is, the gas actually in the tank, plus the gasoline in the pipe. That is, the pipe that runs from the gas tank to just under the gas cap. This space filed, partially filled, or not filled with gasoline leads to what I think of as false high and false low "actual" mpg numbers. On fuelly, one can see a sine wave pattern in a series of fill ups, as the false highs average-out against the false lows and a more accurate overall mpg average emerges.

Regarding (2): Your tire pressures could be too low. New cars as driven off the dealers lot notoriously have other than recommended tire pressures. If so, cold-tire pressures should be reset to at least recommended pressures. I suggest doing this first thing in the morning before moving the car, for accuracy sake; and repeat once a month to compensate for temperature changes, bouncing over bumps, other air loss. (I got my own pressure gauge and portable battery powered air pump.)

At fuelly.com I've recorded every drop of gas that has gone into 3 cars since 2010. A few years ago I looked at my data and memory of many efforts made to get top mpg (without vehicle modification). I sought an answer to my curiosity of how much does doing one thing or another actually impact mpg? Specifically, what are the factors that explain my above EPA mpg figures? My data based intuitive answer, in summary form is below FYI

Consistently above recommended tire pressures 40%
Basic high mpg. driving style (see Hasard below) 40%
Careful tarrain awareness and battery mgmt for top mpg. 20%
__________________
Principles supporting my driving style for even higher EX mpg:
Have the engine operate as little as possible, especially when standing still or moving slowly; while also meeting my demands for power and maneuvering. This means most battery charging while cruising city streets and rural roads, max regen from slowing down and downgrades, and only using heater or A/C when the engine is on for other purposes.

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Last edited by Moviemike; 09-02-2018 at 09:48 PM. Reason: Fix typo
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Old 09-04-2018, 12:57 AM   #6 (permalink)
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Default Fuelly ave mpg is 50.6

So many giving me advice on why my mpg is so low, but not addressing the question about the difference between indicated mpg and actual mpg.

My mpg is based on over 650 miles. Not significantly different than the average of All insight on Fuelly.

I also drive in a hilly area, and Southern California is also known for high speed freeways, where traffic moves at well over 70 mph.

I have been driving for over 55 years, and understand how to get good gas mileage, BUT that still does not explain the significant difference between indicated mpg on the insight ex instruments and my Actual average mpg based on Over 650 miles of driving.

Thank you for all the advice on how to get better mpg.
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Old 09-04-2018, 09:54 AM   #7 (permalink)
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Originally Posted by dave92029 View Post
So many giving me advice on why my mpg is so low, but not addressing the question about the difference between indicated mpg and actual mpg.

My mpg is based on over 650 miles. Not significantly different than the average of All insight on Fuelly.

I also drive in a hilly area, and Southern California is also known for high speed freeways, where traffic moves at well over 70 mph.

I have been driving for over 55 years, and understand how to get good gas mileage, BUT that still does not explain the significant difference between indicated mpg on the insight ex instruments and my Actual average mpg based on Over 650 miles of driving.

Thank you for all the advice on how to get better mpg.
It's an estimate. Here's an interesting link:
Should You Trust Your Car's MPG Display? | BestRide

The above link mentions several other vehicles that were 7-10% off optimistically as well.

I am tracking my fuel economy with Drivvo now to get more accurate measurements. Nothing to report yet. I wish I had started tracking when I got my first fill-up but I only started tracking at my last fill-up.
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Old 09-04-2018, 11:13 AM   #8 (permalink)
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Dave,

As an owner of a 2019 Insight EX and with several fillups already, I can attest to the mpg readout on the dashboard consistently being (approximately) 2 mpg LOWER than my calculations. When I fillup, I fill to the maximum and do not top off. Not sure why your calculation is coming in lower than the readout.
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Old 09-04-2018, 11:52 AM   #9 (permalink)
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The readout is a toy. There is no way beyond making rough guesstamets it can know what the actual MPG is. It is there to help folks adjust their driving style.

Everyone has already told you to check your tire pressures. If this is not something you have paid much attention to in the past, itís time to start.
You need a compressor and a quality tire guage. They need to be measured stone cold in the AM. Being ďof a certain ageĒ myself, I know how hard it can be to get back up once down there, but it will be worth the effort. Dealers are required to check pressures, but they are always doing that warm. So you will have to do that yourself.

I donít think you have enough miles on your Insight to judge how it will really be. These cars are weird and take some adjustments. Old dogs can learn new tricks. But in LA, sometimes you just have drive a forget about mileage.
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Old 09-04-2018, 04:46 PM   #10 (permalink)
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Originally Posted by dave92029 View Post
.....BUT that still does not explain the significant difference between indicated mpg on the insight ex instruments and my Actual average mpg based on Over 650 miles of driving.
The most likely cause is my number (1) below "Gas tank not being filled to the same point each time."
__________________
Principles supporting my driving style for even higher EX mpg:
Have the engine operate as little as possible, especially when standing still or moving slowly; while also meeting my demands for power and maneuvering. This means most battery charging while cruising city streets and rural roads, max regen from slowing down and downgrades, and only using heater or A/C when the engine is on for other purposes.

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