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1 month old sonata hybrid 2013
the displayed mpg does not agree with the actual mpg during fill up
used same gas station, same pump same direction parked when getting gas. displayed 38.1mpg actual 34.5
any ideas
 

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I've noticed the more highway driving I do in any given city/hwy cycle, the more the average is off. I'm over it. I use fuelly to calculate. Sometimes it's 2-3 mpg off, sometimes its 0.5 off. It's difficult to truly measure as each fill up is slightly different from the last.
 

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displayed 38.1mpg actual 34.5
any ideas
Use of 100% (ethanol-free) gasoline will make your trip computer more accurate, when your display is higher than your pencil & paper numbers, since 100% gasoline gives better mpg than 10% ethanol blends.

Go to pure-gas.org for sources, details & a great zoomable map. With no 100% gasoline in Dallas, you'll have to go to Wills Point or Greenville for your 100% gasoline needs.
 

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Use of 100% (ethanol-free) gasoline will make your trip computer more accurate, when your display is higher than your pencil & paper numbers, since 100% gasoline gives better mpg than 10% ethanol blends.

Go to pure-gas.org for sources, details & a great zoomable map. With no 100% gasoline in Dallas, you'll have to go to Wills Point or Greenville for your 100% gasoline needs.
I just checked their site. Nothing close to me. I noticed the stations that list 100% gasoline have it as 92-110 octane. Not cheap. At least least the few stations in my state.
 

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I just checked their site. Nothing close to me. I noticed the stations that list 100% gasoline have it as 92-110 octane. Not cheap. At least least the few stations in my state.
In less than 2 years, listings at pure-gas.org for 100% gasoline have increased by almost 2000 sources. Hopefully they'll get more sources in Massachusetts.

That's how much the "ethanol in gasoline" industry has crippled American drivers. Fortunately, the "ethanol in gasoline" industry is taking hits, lately. First, the EPA is lessening the quantity of ethanol to be blended into our nation's gasoline stocks. Second, Senators Feinstein & Coburn, with much bi-partisan support has introduced a bill to stop ethanol blending. Third, a bill already passed in the House, will stop subsidies to equipment that blends ethanol into gasoline. Please support those bills.

Three little & big beginnings have the "ethanol in gasoline" industry retreating.
 

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Yeah, mine is off about the same after approximately 6400 miles. I reset my mileage manually after every fill up and log what I have for calculated MPG with my fuelly account and they're consistently off.

Lightsong, how does fuel to ethanol ratio have anything to do with how the car calculates MPG? The computer knows how many miles are being driven, the gas flow rate and gallons consumed. I think it's pretty obvious Hyundai is hoping that there are enough people out there who don't calculate out their MPG and use the displayed number when they talk to their friends, thereby getting word of mouth testimonials to an inflated number.
Don't get me wrong, I completely understand the loss of MPG when using ethanol. I'm not arguing that.
 

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Guys your HSH odomertor is probably off by about +3 mph and your calculated mpg is -3 mpg so you are traveling about 3% further than displayed. So the indicated mpg is fairly accurate. Check your odomertor by going 60 mph and use those mileage markers to Guage or put a Garmin GPS device and check your speed with it. My Santa Fe going 60 mph will display 57 mph on my Garmin.
 

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Tom, I drive by these solar powered radar guns that tell you the speed. So you're saying if my speedometer says 40 the radar display will read 37?I'll test tonight on my drive home.
 

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Tom, I drive by these solar powered radar guns that tell you the speed. So you're saying if my speedometer says 40 the radar display will read 37?I'll test tonight on my drive home.
It might work out that way so let us know what happens. I remember when we were leaving CA I had a Garman in the HSH and it displayed the speed 3 mph lower than the cars display. This is probably a good thing as it might keep you from getting a speeding ticket.
 

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I tested it out - It appeared to be so - it clocked me at 37 mph when the speedometer read 40 mph (I have some doubts that I was exactly - I need to test again), I'll update tomorrow when I go back to work and test again.
 

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Guys your HSH odomertor is probably off by about +3 mph and your calculated mpg is -3 mpg so you are traveling about 3% further than displayed. So the indicated mpg is fairly accurate. Check your odomertor by going 60 mph and use those mileage markers to Guage or put a Garmin GPS device and check your speed with it. My Santa Fe going 60 mph will display 57 mph on my Garmin.
Hey Tom

My car does the same regarding the odo/gps variance, and like you I also have a Santa Fe that does the same. Similar with the displayed mpg/L/100km, they both somewhat exaggerate the cars performance.

It seems to me those two variances add up to a larger negative, rather than a more positive outcome in performance.

Regardless, I'm more than satisfied with the power and performance of both vehicles. Have the HSH on fuelly, and the overall is 6.2l/100km. That's about 37.8mpg/us which is incredible in the mountainous terrain around here.

Barry
 

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I compare my speed with a GPS. This is the most accurate way IMHO. And I also found out it is the instrument cluster speedo they use for fuel calculation, not the odo. The speedo and the ECU reported speed are not the same either.

If the instrument cluster speedo is accurate you mpg display will be more accurate.
 

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Just too many variables for me, fellas. Instrument cluster vs. odometer vs. pump display vs. GPS vs... Before long, this begins to sound like a Pay Per View wrestling event full of headliners. :grin: A different champion every week.
 

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Yes there really is only one way and that is had calculation. If you do this with every fill you will notice if something is quite different.

I over 95K miles on my Accent it has always been between 36 and 42 mpg when figured by hand. The factors are usually speed and weather as most of the driving terrain and routes are the same.

I would worry the least about pump variation. At least in Illinois most service stations don't mess with that. Though I'm sure it could be done. One quick way to check is to stop the pump at 10 gallons and look at the price. I suppose that could be messed with too.

I would say I have yet to see a factory speedometer or odometer be accurate though.
 

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I was tracking this late last year and was recording what the display (aFCD) indicated vs calculated. Even adding in 3% for odometer error (which would add about 1 MPG to calculated) doesn't make-up the difference. It's not too far off - usually within 10%. But the aFCD is always a bit optimistic.

 

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When I went to bigger tires on My Gen Coupe this helped get the speedo more in check. Went from reading +2 mph to reading almost right on when compared to the GPS.

This also corrected the mpg display. It was usually +3 mpg on the happy side. It is no much closer to the actual calculated value, withing .5 mpg.

But as I said the odo and ECU reported mph are even the worse off. My odometer correction is x1.046 for calculating the mpg. This is figured from the actual mile total of the gps loop and the odometer reading.
 

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I would say I have yet to see a factory speedometer or odometer be accurate though.
I haven't had time to compare my HSH to my GPS but when I did compare the speedometer on my 2013 Accent to the GPS it was off 8 kph at 100 kph BUT it i hit the Average Speed reset on the display the initial reading was right on the money.
This was all done on flat terrain and on cruise control.
I never really compared the mpg that much since it is only a number and my driving as well as other conditions outside of my control will dictate the results. The speed is a different case for me due to trying to run as fast and still stay reasonably legal.
I kept forgetting to get the dealer to check the speedometer but I do remember reading that the error seemed to be within their plus or minus allowance. I thought the allowance was pretty shitty!
In doing the comparison between the instant average reading and my HSH speedometer it appears to be within 1 kilometer or 2 which would be a huge improvement over the Accent. I will compare it to the GPS next week and see.
I know that all motorcycle speedometers are suppose to be 10% optimistic and that seems to be true with my 2004 Burgman 650 until I reach over 130 kph and then it seems to be correct according to the GPS on it.
My 2001 Jeep Cherokee and my wife's 2006 Dodge Caravan are both right on the money. I bought both of them used from our military so I don't know whether there was some requirement that they be accurate, neither is or has anything special but you never know what was in the original purchase requirements.
 

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I just bought a 2013 Sonata Hybrid and have done about 320 miles and just over half a tank left so by my math I am not doing bad but a majority of my drive is highway. I have owned a lot of cars and their little computers are always optimistic when it comes to miles to the gallon but closer to accurate with miles to empty. I figure after a good couple of tanks the computer will have a better time figuring my distance to empty out right now its kinda funny because it stays at the same number for a long time since I am doing a lot of highway. Bottom line I bought this car for it's mileage and features so I plan to drive it like a hybrid and see what I can get out of it.
 
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