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OFFICIAL Fuel Mileage Discussion Thread

301K views 2K replies 262 participants last post by  rgolesh 
#1 ·
In our effort to keep things concise, all posts concerning fuel mileage will be posted here. I apologize for the elimination of the other thread; it is archived for your reference (combined with steering wheel peeling thread).

To summarize what many of us have discovered in our discussions on fuel mileage:

Fuel mileage is a common complaint on this subforum, and can vary depending upon geographical location, outside temperature, wind speed, elevation changes, personal driving habits, type of road, etc. Many members claim that fuel quality also affects mpg.

The 40-mpg claim is a projection for freeway driving. Your overall tank average is that of all your driving, so unless you only drive gently on perfectly flat freeway, it will be HIGHLY unlikely that you will get a combined tank average of 40 mpg.

The read-out on your dashboard may not reflect perfect accuracy, so it is recommended that you still manually calculate your own fuel mileage if you prefer a more accurate readout.

Most of you seasoned members already know this, but for anyone new to the Elantra and/or to the forum, please post all your questions here before starting a new thread on the topic. Thanks a bunch! :D
 
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#3 ·
One other point to add to any fuel economy thread - Hyundai odometers read "low", not recording all the miles you drive. So if you prefer the "hand calculated method" of dividing miles on your trip odometer by gallons counted on the pump, be aware that the displayed "miles" is too low, and that means your calculated mpg will be lower than actual. In the Elantra, only 96.6 miles out of every 100 driven are being counted, although that number varies slightly based on which tire/wheel combo you have on your Elantra.

If you don't want to fuss with correcting the pessimistic odometer, just take your hand calculated mpg and multiply it by 1.035 to get the corrected mpg.

Example:
309 miles shown on Trip "A" is actually 319.8 miles.
The pump says 8.0 gallons added.
Hand calculated: Trip "A" divided by gallons added = 309 / 8, or 38.625mpg
Corrected: (Trip "A" x 1.035) / 8 = 39.977

Alternate: 309 / 8 = 38.625 - hand calculated mpg. And then correct it - 38.625 x 1.035 is 39.977
 
#7 · (Edited)
One other point to add to any fuel economy thread - Hyundai odometers read "low", not recording all the miles you drive.
What is your source for this?

Most odometers are fairly accurate to within +/- 2% or so. They have to be because vehicle certification regulations require it. I'd be surprised if Hyundais are any different, especially since it would lengthen their warranties and under-estimate their gas mileage.

- Mark
 
#5 ·
Yes, actually. Your 100,000 mile powertrain warranty lasts an actual 103,500 miles. :) When correcting the distance, the dashboard mpg meter is actually closer than people realize. It's still not on target, and it can be thrown off by wild variations in city/highway driving mix, but it is closer than you think.
 
#6 ·
Speedometer Odometer Auto part Gauge Measuring instrument
Taken a couple of weeks ago... Over the course of six days, mostly highway miles obviously. But still, I'm happy with my mileage :p This is no fluke, either, as my display currently reads 44.2 mpg avg. after 1/2 tank of fuel. It's been around 40 avg. all summer for me! Admittedly though, my grandpa thinks I drive like a grandpa... haha
 
#1,491 ·
View attachment 55261 Taken a couple of weeks ago... Over the course of six days, mostly highway miles obviously. But still, I'm happy with my mileage :p This is no fluke, either, as my display currently reads 44.2 mpg avg. after 1/2 tank of fuel. It's been around 40 avg. all summer for me! Admittedly though, my grandpa thinks I drive like a grandpa... haha

What is your mileage with the A/C running versus when it's off?

Also, what's your tire/wheel combo?
 
#8 ·
The few times I calculated by hand, my MPG numbers came out to within a tenth of what the trip computer was telling me, so now I'm content to go with its figures.

I've put 11,000 miles on my 2012 Elantra GLS Preferred since I bought it last October, and currently I'm getting between 30-33 combined MPG and 37-38 MPG on the highway, in hundred-degree Midwestern heat and with MAX-A/C running almost constantly. Which I'd say is pretty good. No complaints here about my mileage.

With decent (ethanol-free) gas in the tank and cooler spring temperatures, I've hit the magical forty MPG mark in spirited highway driving. OTOH, last winter, between letting the car idle to warm up and slow driving on slick roads, I had a couple of tankfuls where I averaged 25-26 mpg.

Like they say: Your mileage may vary.

There's a guy on another forum who's been kidding me about my Elantra's "inflated" mileage figures. He has a Prius and a new 2012 Ford Focus, and drives the Ford when he feels like taking a spin in an actual car and not an appliance. He claims an average of 33 mpg with the Focus.

He's also had to take the Focus back to the dealership within the first couple of months he's owned it, with a suspension problem. Something about the front struts and springs needing replacement.

And meanwhile my little black raven just keeps chugging along... :harhar:
 
#9 ·
Admittedly though, my grandpa thinks I drive like a grandpa... haha
I'm a grandpa, what's wrong with that? 

I have no complaints with my mileage. Not only do I get great mileage, IMO, but I get it driving around town "in style!" 
 
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#10 ·
I'm a grandpa, what's wrong with that? 
:D hahaha absolutely nothing, I just wanted to make it clear that I do have to "work" to get the kind of mileage I get... although, a majority of my summer driving is done @ 60 mph with the A/C on and/or windows open (yes, both haha), so it could be even better yet. Speaking of that, has anyone noticed a huge difference in mpg with the A/C on or windows open? It only seems to hurt my mileage by 1 or maybe 2 mpg... pretty insignificant and certainly not worth sweating over IMO.
 
#13 ·
Dozens of cars, and many dozens of other owners of various Hyundai models, with a forum search here showing some others who stumbled across it on their own. Feel free to do your own test, or to not believe and use your trip odometer as is. It's not important for people who don't calculate fuel economy to the nearest tenth, although people who record mileage for reimbursement from their employer will be shorted a little.
 
#15 ·
There is a 1.5% difference in rolling dia between the 3 factory tire sizes. This can easily account for some discrepency in odometer readings. Then figure another 2% difference between a new tire and a worn tire. So we can see up to 3.5% difference. Which tire and under what wear level should the odometer be be "right"? My guess is that Hyundai calibrates the odometer for the smallest tire when worn to 2/32nd inch tread. This way there is no question when you go in for warranty work. IF it read 100% accurate when new, then, as the tire wore down, the miles indicated would add up quicker than actual miles driven. Not covering a repair at an idicated 100,509 miles, when the actual might have been 99,627 miles might be grounds for a lawsuit.
 
#16 · (Edited)
There is a 1.5% difference in rolling dia between the 3 factory tire sizes. This can easily account for some discrepency in odometer readings. Then figure another 2% difference between a new tire and a worn tire. So we can see up to 3.5% difference.
Your figures sound unusually generous, but even if they are correct, I must point out that this would mean that most of us would have odometers more/less in the middle of this range of error (say around 1.7%), not at the 3.5% extreme where all factors break in one direction.

Not covering a repair at an idicated 100,509 miles, when the actual might have been 99,627 miles might be grounds for a lawsuit.
To support your point, Honda recently settled a class-action lawsuit where it was accused of deliberately having odometers read higher than actual. Honda's defense was that they were within established industry guidelines. Their problem was that their own documents showed that they were deliberately biasing the odometers high with tolerances of -1% to +3.75% with obvious benefits of reduced warranty, lease terms, etc. They've since said they now are tolerancing odometers to be centered on zero error. (Note that even though they paid out big money to settle this lawsuit, they are not erring on the conservative side to tolerance their odometers to read low so they never read high.)

I'm still very skeptical that Hyundai is going completely against the grain in the car industry by being so ultra-conservative in favor of the consumer when there is no regulation that says so and there is no general industry guideline that says that to never read high, you must bias your odometer low. I applaud them if they are, but I've never heard of this from any other source other than this single poster here.

I am curious to see what mine says.

- Mark
 
#17 ·
I was getting 40+ mpg during highway driving before I bought new tires, but I'm getting ahead of myself.

After one of my POS OEM Continentals blew out its sidewall while sitting at a redlight, I was forced to replace all the tires with whatever the rats at the stealership had in stock. I now have 4 BF Good-for-Nothing Wrench G-Force Sports which barely let me get 30 mpg on the highway.

If I really push it with these tires I can see 35MPG. Really pushing it with the OEMs got me 50 mpg.

I'm really pissed about this since I didn't know I need special tires to get 40mpg with this little car. I now have 5k miles on the new tires and mpgs is really not improving.

My last Hyundai.
 
#18 ·
It makes no sense to me that you are faulting Hyundai for this. It is so widely known that Hyundai uses "low rolling resistance tires" in order to achieve the MPG figures that ARE possible. If you would have read the owners manual, you would have been aware of this.

You didn't have to go to the dealership to get tires. In fact, most people would highly recommend against it. You could have shelled out and bought some low rolling resistance tires, but you didn't. Tires fail from time to time; it's a fact of driving.

Research your purchases. Know what you are buying. Make mistakes and learn from them; don't place blame where it isn't due.
 
#26 ·
Just got a brand new 2013 Elantra Coupe GS (AT) from the dealership this past weekend. I've put about 100 miles on the car. The tank read full when I got the car. After 100 miles of city driving (I've been ginger on the accelerator) w/ Eco engaged.......it says I'm down to a half tank of gas (still first tank) and the mpg meter says I'm only getting 18.8 mpg. Needless to say, I'm concerned. I know there are a variety factors that can affect fuel mileage, but I really wasn't expecting anything (allegedly) this low.

Has anyone else had any experience with the car reading unusually low mpg when the car is brand new? Is this something that should calibrate its way out over the course of a couple tanks of gas or should I be going back to the dealership to get things checked out? Recommendations?
 
#30 ·
Your low avg MPH is indicative of lots of stop and go driving which kills your fuel efficiency. And you probably have the A/C on.

If you want to see if your car is capable of the EPA 40/29, test the car the way the EPA does (or as close as you can make it).

The HWY test is a 10.3 mile run where the avg MPH is 48.3 and the top speed is 60.

The City test is an 11 mile run where the avg MPH is 21.2 with a top speed of 56 MPH. Your avg idle time at stop lights should be around 14 sec at 23 stops.

Detailed Test Information
 
#29 ·
asalter,

First off, welcome! We haven't had many Coupe owners yet, so I'll be interested in what you have to say.

I have to tell you, it seems like the slower I drive my Elantra under around 45 or 50 mph, the worse gas mileage I get. I live in a very hilly area, and even now, with over 14k on the ODO, it's not uncommon to get a tank average of under 20 mpg if I am ONLY driving around my area. It's hard to take a picture of it, I live on this giant hill called "Mt. Scott," and the road to my house literally goes straight up it without any switchbacks. Whenever I go on it, my gas mileage tanks. Now, if I go out on the freeway, my tank average will rise significantly, as my car really does get high 30's to 40's on the freeway going the speed limit.

Your mileage will improve as your car breaks in. I tend to be a bit of a lead foot at times. I've calmed down for the most part, but sometimes if someone pisses me off...well, you get the picture. So I don't always get the best read-outs, either. My best advice is to go easy on that pedal! :D
 
#31 ·
Got my GT friday, already put 400km on it. Basically have found the sweet spot is between 90-100, which i suppose is standard for most cars. First long drive I averaged 7.2, that was going 110 ish with cruise control on and windows down. (150km drive) On the way back I stayed between 95-100, and slowing down on large hills to keep rpm around 2200, was able to finish with 5.4 seeing as low as 5.2.

Third run today, a 120km drive through a very hilly road driving same as before, 95-100 and slowing on hills, averaged 6.4

Hyundai rates highway at 5. All in all not bad, I am happy to know I can almost reach the EPA. I also live in BC which is quite hilly/mountainous so would think the ratng would be easy to hit in somewhere more flat.
 
#32 ·
First off, welcome! We haven't had many Coupe owners yet, so I'll be interested in what you have to say.
Thanks for the "welcome"....I've found the forums to be quite helpful. With the exception of the mpg concerns, I really do love the coupe. For being a 2 door, there is a remarkable amount of cargo and rear passenger space (no issues with feeling cramped in the back seat.....although I am only 5'10" B)). I also like that many modern features (bluetooth integration, heated seats, etc.) come standard on the Coupe GS. Oh, and the car handling is fantastic.

I have to tell you, it seems like the slower I drive my Elantra under around 45 or 50 mph, the worse gas mileage I get.
I have only had a reason to take it out on the interstate twice since purchasing it......and even those runs were only a couple miles. I live in an urban (although relatively flat) environment with a streetlight or stop sign on practically every corner.....so I guess that accounts for a lot of the "sub optimtal" mpg. I'll continue to go easy on the accelerator and hope that I'm pleasantly surprised if the readings callibrate to something more expected over the next few tanks of gas.

Your low avg MPH is indicative of lots of stop and go driving which kills your fuel efficiency. And you probably have the A/C on.
Both are true. I guess I just hoped I would be getting closer to the "city" rating.

If you want to see if your car is capable of the EPA 40/29, test the car the way the EPA does (or as close as you can make it).
Good suggestion. I'll try to make time to do this test in the next day or so and hope for good results. I just wanted to make sure there wasn't something wrong I should get looked at. This will be a good way to tell.
 
#33 ·
You need to run a few tanks through the car before making any overall judgment on mileage. For one, the dealer probably didn't get the tank completely full when you bought it - the gage will stay on F for a good 30-40 miles before it begins to move. Second, the gage is not a precision instrument where you can be making accurate estimates of fuel used from an intermediate position on the gage. Third, you need to put a few break-in miles on the car.

My guess is that once the noise settles down, you'll be getting what the rest of us are, which isn't matching the EPA numbers for the most part, but is Okay - low 30's in mixed driving, but mid-20's when the chips are down.

IOW, don't panic yet!

- Mark
 
#35 ·
I've put 15,240 miles on my 2012 in 3.5 months. It an automatic. I can get 37-39 mpg average tank full if I keep it at 55-60 on the highway USING CRUISE CONTROL. 70-75mph I can be 35-37. using cruise control. I even use cruise control around town on 25mph roads, 45 mph roads, it helps a lot with the town mpg's.
 
#36 · (Edited)
I finally got out and did a couple of odometer accuracy runs on the interstate using mileage markers. I must eat at least a small helping of crow and acknowledge, much to my surprise, that the odometer on my 2013 Elantra GT does read low, although not the 3.5% dmlexpert says is typical.

My estimate of odometer error: 1.7% low (odometer reads less than actual). I made two runs of 18 and 12 miles and while I'd like longer runs for accuracy, they did match up fairly well. I'll do some hundred mile long checks on a trip coming up in October.

I'm impressed that Hyundai has erred on the conservative side with respect to warranty and that my gas mileage is being slightly under-estimated. Which remains a little less than I had hoped at about 29 mpg, with perhaps 1/3 on the highway.

- Mark
 
#38 ·
I finally got out and did a couple of odometer accuracy runs on the interstate using mileage markers. I must eat at least a small helping of crow and acknowledge, much to my surprise, that the odometer on my 2013 Elantra GT does read low, although not the 3.5% dmlexpert says is typical.

My estimate of odometer error: 1.7% low (odometer reads less than actual). I made two runs of 18 and 12 miles and while I'd like longer runs for accuracy, they did match up fairly well. I'll do some hundred mile long checks on a trip coming up in October.
Mark,
I still have the numbers for my Elantra that I used for calculations, and I'd add that you'd want to go for at least 50 miles to make sure you're spot on, since shorter distances can skew the results so far. Ex: Driving 10 miles while Trip-A reads 9.7 shows as 3.1% off while 9.8 would be 2% off. But reading only tenths, the resolution isn't fine enough to see where it falls in between unless Trip-A ticks to the next number as you pass the mile marker. In my own Elantra, two of my tests included: 54.1 miles shown after 56 miles on mile markers (1.0351%), and 64.7 miles shown after 67 miles on mile markers (1.0355). The difference in those two numbers amounts to 26 inches, so it seems pretty repeatable. The error on the Limited is a bit smaller (in the upper 2% range), so I have to wonder if your GT has the 17" wheels. If so, your offset would be smaller and you may be close to actual offset in that one test.
Back to the original point, the odometer, Trip-A, Trip-B, and any aftermarket gage that reads data from the ECM will very likely read "low" and that lowers calculated fuel economy. Sure, it's not much, but it makes a difference for people who calculate to the nearest tenth and look for any improvement in mileage.
 
#40 · (Edited)
My Stats so far..

I live in Texas, mostly flat with very hot to mild weather most of the time.. rarely below freezing temperatures. My daily commute is about 70/30 hwy/city. I average 65-75mph freeway, 30-40mph city between stoplights. I don't accelerate quickly and drive very efficiently.

2012 Elantra limited w/nav
Nitrogen filled tires & no Spare in the trunk

Total miles driven: 12,436
Avg. miles per tank: 309.58
Avg. gallons per fill up: 10.46
Avg. MPG (dashboard CPU): 31.64
Avg. MPG (actual): 29.56 (CPU scores +2.08 MPG on Avg.)
MPG ECO button on: 29.59
MPG ECO button off: 29.53
MPG K&N air-filter: 30.0
MPG OEM air-filter: 29.63
MPG K&N w/ECO off: 30.08
MPG K&N w/ECO on: 29.85
MPG OEM w/ECO off: 28.45
MPG OEM w/ECO on: 29.69

I threw out the 1 highest and 1 lowest figures on each category to get a more accurate average.

There you have it! Nowhere even close to the claimed 40mpg's or even the average 33mpg's! I still like the car though.
 
#42 ·
So I did an out and back trip with my E monday/tuesday. Out on my idaho gas bought at safeway I struggled to get 31.5 which in the past is pretty much normal for my E even when cruising steadily at 60. Coming back on Oregon Shell gas I avg 39. Yes, there was a bit more downhill coming back but I have NEVER seen 39 mpg or close to it on my dash before. I always thought gas was pretty much a generic deal with various companies adding their "special" ingredients. Maybe gas is not the key but it was the largest single variable I can think of.
 
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