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Aaron Gold

Elantra MPG... or not

By March 31, 2011

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The other day, I asked you to predict the fuel economy on our Elantra road trip, and we'd see who came the closest.

I was going to post the results today, but... well, there's been a problem.

It seems that the Elantra's trip computer automatically resets the average MPG when you fuel up. It would have been great if I had figured this out BEFORE I stopped for gas just 50 miles shy of our destination. But I didn't.

Worse yet, I can't tell you what the fuel economy was just before our fuel stop, because I had the display set to Distance to Empty.

Sigh. Sorry 'bout that.

I can tell you that as we left the hilliest sections behind, our fuel economy was in the mid-30s, and for the last section of the trip -- flat as a board, with speed limits dropping fro 75 to 55 -- the Elantra was nearing 42 MPG.

I can also tell you that the 2011 Elantra is a lovely car to take on a long trip. It's quiet, the seats are comfy, and the ride is smooth. Even for a Hyundai fan like me, it's hard to believe you can get a car this nice for $15,550. (The car I'm driving, an automatic GLS with the Preferred Package, iPod cable and floor mats, lists for $18,445.)

Anyway -- let's try again, shall we? I'm driving home next Monday. I always seem to get better fuel economy on the ride home; the hills are a bit more gentle. You can stick by your old guess or post a comment with a new one, and I'll try my best not to screw up this time! -- Aaron Gold

March 31, 2011 at 8:44 am
(1) CL says:

And you believe what their trip computer tells you? I’ve got an Acura and it’s consistently, shall we say, optimistic…

March 31, 2011 at 11:25 am
(2) Aaron Gold - Cars Guide says:

I do, CL. In my experience, they are fairly accurate. Doing it manually can be pretty difficult, especially if I’m going for accuracy with just 1 or 2 tanks. Every nozzle clicks off at a different time, so I have to top off the tank until I can see that the filler neck is full and the gas isn’t draining back into the tank. That can take 10 minutes or more, not good at a busy gas station (let alone a freeway gas station where I’m paying 80 cents/gallon more than the going rate). It’s also horrible for the environment. You need to do a *lot* of fill-ups to get an accurate number.

The way I see it, the trip computers are pretty precise — they are drawing their data from the engine ECU, which has to meter the fuel precisely. At the very least they have to return an accurate DTE number – imagine if your car says you have 20 miles to empty and it runs out of gas in 10…


March 31, 2011 at 8:45 am
(3) Brian says:

I should have warned you about that. I only track my fuel economy from tank to tank anyway, so I don’t wory about it. However here’s something even more annoying… The distance to empty on our Santa Fe stops counting at around 50Km to empty. Drives me crazy becuase I don’t know how long I have to get to the gas station. (My wife doesn’t care becuase she would rather I “just stop and get gas already”).

Are you watching the ECO light at all? Our sales person said it just goes own to show you when you are driving below certain MPG. However I’m not sure. In the mountains, it tended to be on even though I was not in overdrive going uphill. Conversely, it would go out when I was travelling downhill at 75mph with my foot off the gas.

Incidentally, Elantra is rated at 58MPG here in Canada, which is about 48MPG in US gallons. So I’m not surprised you are getting better than 40.

March 31, 2011 at 8:57 am
(4) August-Az. says:


I think the Elantra will average about 42 MPG. These cars are notorious for delivering more than the EPA estimates. This was my original prediction.

March 31, 2011 at 9:33 am
(5) Jeff says:

I think we all can agree that I won.

March 31, 2011 at 11:11 am
(6) Steve in GA says:

I’m surprised that you actually seem to rely on a trip computer to give you reliable mpg information. The trip computers on my cars have never been more than an interesting curiosity, and are usually off by at least 2 mpg.

The only way to get the real scoop on mileage is the old-fashioned way: divide the number of miles you have traveled by the number of gallons of fuel used. I do this on every tank. (My family says I have OCD about gas mileage.)

March 31, 2011 at 11:24 am
(7) Tom R says:

I agree with CL. I’d suggest doing your own calculations and then comparing it to the car’s trip computer. Might be interesting.

March 31, 2011 at 2:16 pm
(8) Ross says:

I’ve found trip computers to be precise but inaccurate. My MS3 reads about 2mpg high, but it is consistent, I just have to remember that it’s lying to me.

When I go on a highway trip it averages 28, but when i do the math I get about 26.
Around town it says about 19.5 or so, but it’s closer to 17.5-18.

March 31, 2011 at 3:21 pm
(9) Paul says:

Brian, not sure but maybe the air being thinner in the mountains has an effect on fuel consumption, as the engine has to work harder to aspirate?

March 31, 2011 at 4:31 pm
(10) Carter says:

I think all of you guys are forgetting one important thing. You’re not factoring in the “human error” element, which is generally accepted in the electromechanical industry to be about 5-7%. Use that, and suddenly your precision fuel calculators (which I would trust over almost any human estimation) aren’t so far off. In fact, some would be dead-on accurate. As Aaron alluded to, unless you are getting your fuel from the exact same pump everytime, and stopping exactly when the nozzle cuts off, your numbers will be skewed.

March 31, 2011 at 5:04 pm
(11) RK says:

You can still compute your MPG the old fashion way. Just subtract your beginning mileage from ending mileage and then divide by number of gallons used. If you did not keep that record either, perhaps you can Google the distance using mapquest. I would hope you kept receipts for fuel otherwise all is lost!

March 31, 2011 at 6:49 pm
(12) Ross says:

@Carter, I always keep a little notebook in my car and record odometer readings and gallons bought.

Gas pumps here have to be certified every two years by the state bureau of weights and measures.

Odometer regulation is very strict too, such that an 5-7% difference would be amazing to me. Seeing has how the punishment for altering them is pretty high here. Of course if you change tire sizes or gearing, you’ll mess them up. I run stock tires on my vehicles.

I can tell you with a high level of confidence, that the computer in my car is not accurate.

Just my 2 cents, take it or leave it.

March 31, 2011 at 8:59 pm
(13) Mike in Minn says:

My 08 Nissan Altima was off by 2.5 mpg on average. It nearly always showed that the car was getting better mileage than it in fact was. My friend has an 06 Maxima that has the same problem and by the same amount even though it has a different engine. My 07 Jeep Wrangler Unlimited and 09 Pontiac G8 GT, on the other hand, are much more accurate. They are usually only off by .5mpg and usually the vehicle has done better than the computer says. So I’ve seen it both ways.

Averaging over many tanks is the best way to minimize human errors; an owner has an advantage over a journalist who has to go through the convolutions Aaron mentioned.

March 31, 2011 at 10:17 pm
(14) Alex says:

I have a 2011 Sonata, which has basically the same trip computer as the Sonata (it also resets when I fill up). After 9000km, I found it to be giving me lower fuel usage that what I actually calculate:
City driving: trip computer gives me 9.5 to 10.5l/100km, I calculate at the pump 11-12l/1000

Highway driving: trip computer: 6.7 to 7l/100km
calculation at the pump: 7.5-8l/100km

If the issue was when the pump “click” it will be sometimes over, sometimes under, but in this case it consistently better performance… you wonder if Hyundai makes it a bit optimistic

April 1, 2011 at 3:47 pm
(15) borrisbatanov says:

Porsche already has a pretty poor reliability record. Why would it want to model itself after Toyota or Honda, both also with poor reliability.

The days of Honda and Toyota making reasonably priced cars that lasted forever are long gone.

Old Joke:

Q. How do you tell the difference between a Porsche and a porcupine?

A. With a porcupine, the prick is on the outside.

April 4, 2011 at 11:58 pm
(16) Hawaiian Don says:

I just returned from an overnight trip from San Diego to Bullhead City, AZ and back in my VW Golf. According to my mileage on the trip odometer, it was exactly 33MPG. However, the total miles driven on one tank of gas was 520 on a 14.5 gallon tank equaling 35.86 MPG. That’s a discrepancy of nearly 3 MPG. The only number I’m reasonably sure of is the second calculation, because I filled the car both times right to the last drop and filled the car each time with only 5 miles remaining till empty.
So do I feel the trip computer is accurate???
Sort of!

May 8, 2011 at 9:42 am
(17) Masa says:

I have a 2011 Elantra with a GLS trim, and unless my math is wrong I’m no where near the 48 MPG. :( I typically get 25-30 MPG – driving at an average of 60 Mph. (highway driving)

I’m well under the estimate. I used to drive a Saab 94 900 s yet at highway speeds, I was able to go from Toronto to Montreal and back on a tank and a half of gas. The mileage was unbeleivably good (especially the pocket book!!)

Any thoughts on why I’m experiencing poor milegage with the Elantra?



May 31, 2012 at 5:37 am
(18) Robert says:

EPA tests are done without any ethanol. They are using 93 octane. Average speed for highway tests are 48mph, and max out at 60mph. In fact EPA doesn’t test all vehicles, they DO take manufacture’s estimates.

August 21, 2012 at 7:12 pm
(19) brad says:

I’ve kept records of every drop of fuel put in my 2013 Elantra, after 3400+ miles the computer is consistently 2-3 mpg high. The only reliable method I’d the old fashion hand calculation, or fuellog app.

October 3, 2012 at 9:26 am
(20) steve daniel says:

The 2 mpg number may be right because Hyundai takes advantage of allowable speedometer error and reads 2% low. This means that you are going 2% slower than you think you are and 2% farther than you actually travel. I realized this when I was checking the Navigation system against my old Garmin (which also can tell you mph). I also have asked other Hyundai owners and they confirmed it. In my case, the 33 mpg I thought I was getting is actually ~ 1 mpg high.

October 3, 2012 at 9:30 am
(21) steve daniel says:

Sorry, but in my post I meant to say the speedometers are 5% off – not 2%.

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