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I thought I'd improve my mileage considerably on my wife's AT4 Hyunda Elantra driving down to my mom's in Southern CA and back over Christmas. Instead, I hit the mileage wall. I'd gotten 38.6 mpg in October on the same trip just using cruise control at 55 mph. This time, I drove most of the trip with CC set at 50, DWLed up hills to keep the transmission from downshifting as much as possible, and coasted NICE-on down hills with some P&G down the hills. It didn't help much. Instead of 38.6, I got 39.6 mpg this time.

I attribute the minimal mileage gains to a mostly flat route, much colder temperatures (about 20 degrees F cooler), and having to run lights and windshield wipers about 20% of the time. I had to throw out the tank mileage driving down, as I didn't fill the tank full at the start of the trip.

I was hoping to top 150% of the combined EPA mileage estimate for her car (27 mpg), which is 40.5 mpg. I didn't make it. I guess I'm going to have to wait until Summer and warm weather to beat it.

Well getting another mile in even worse conditions is a large improvement. Like you say, it'll be more apparent in warmer weather when you try again.

What do you mean by pulse and glide down hills? Do you put it in neutral?

My P&G down hills was usually done on slight downhills to get more rolling distance, or to get me over the crest of the next hill.

Sounds like you did very well considering the worse conditions. I'm assuming that with the wipers on the roads were wet which will take a hit on your mileage as well. I've noticed I can get worse mileage on a warm wet day than on a cooler dry day.

Sounds like you did very well considering the worse conditions. I'm assuming that with the wipers on the roads were wet which will take a hit on your mileage as well. I've noticed I can get worse mileage on a warm wet day than on a cooler dry day.

I agree. Wow I'm impressed with SentraSE-R's 39.6!!! with those conditions and an auto!

I can also understand your frustration SentraSE-R. 40 is so close….

I've never managed to beat 38 in one tank.
I'm in an '07 Elantra AT4, and even keeping her shy of 55 for an entire tank, my 70/30 hwy/city mixed driving wouldn't break 38..
I'm thinking that you're close to the wall for an AT Elantra, given that you can't go ICE-off without a stick in this vehicle.

Thanks for all the compliments. I agree, there wasn't much more I could have done on that trip, other than jettison the wife, dog, passenger and rear seats, spare tire, and Christmas presents ;), or find another route where I could poke along at 40 mph.

While there might have been gains at 40 vs 50, you'd spend longer driving in the wet...I don't know if the increase in FE due to lower speed would be enough to offset the additional time spent driving in bad-FE wet conditions?

Drove my wife's car last night about 120 miles, with her and an additional 300 lb passenger. Got 36.7 mpg on the first half of the trip, and 37.2 mpg on the return trip with CC at 55 mph, and some P&G NICE-on on downhills. Both legs of the trip, the mileage started slow and never rose to 38 mpg. I realized later that I'd left the mileage correction at +2 from my Nissan, when it should be -1 for the Elantra. That 3% miscorrection meant that I really got an additional 1.1 mpg or so, but 38.0 mpg is still on the wrong side of the wall. I'm happy with that, considering the extra weight we were carrying.

If her car's mileage goes up 15-20% in the summer, I guess I can hope for 44.8-46.8 mpg. but if it only goes up 10% or less (to 42.9 mpg), I'll be disappointed.

I drove her car again on a long trip, this time nearly 500 miles down and back to the Central Valley. The SG estimated only 36.5 mpg over the 494 miles. Conditions weren't the best for good mileage, as there was water on the road on the way down, I had to run with lights and wipers on over about 25% of the trip, and there was a slight headwind on the return trip. My only hope to salvage decent mileage was if the SG needed a recalibration. That was the case, as my calibration went from 13.5% to 11.2%, and actual mileage based on the fill-up was 37.85 mpg . That's still the worst mileage I've gotten from her car on a long trip. Summer can't come soon enough. I just hope that running the AC won't take away any gains I'll get from lower rolling resistance.

The drive was pretty flat, as you might expect. I mostly drove with CC at 55 mph, NICE-on coasting down the steeper hills. I haven't found a high-speed P&G routine that works for her car.

If it's anything like the 99 Elantra, A/C is a killer on mileage. If I can get a really flat interstate (like I95 from Virginia to North Carolina), and set the cruise between 55 and 60, I can keep an average of 42 MPG or so. I wonder if it's just that the Elantra has gotten that much more bloated over the years?

The Elantra has gained about 160 lbs between our old 2000 and our 2006, but its overall top gear * final drive ratio is 2.68 in 2006, and was only 2.50 in 2000. So its lower mileage seems to be a combination of weight and gearing.

Don't beat yourself up too much. Also remember that you are likely fighting winter formulation in your gas tank too. I would say that all things considered you did well. You can always try not doing anything at all - deflate your tires to door placard, drive posted maximum limits, don't P&G, don't dfco, don't DWL - and see what your baseline is. You may feel a more realistic sense of accomplishment.

Ever since I stopped my ICE-off P&G hypermiling in my Paseo and just try to keep up with traffic now for safety, I have a pretty good idea of how well I was doing in the first place. Right now - with tires at 50psi - I'm pulling just right around EPA most of the time. Before even in the coldest days of winter I was averaging around 44mpg. That was abysmal compared to my summer highs of 53mpg, or so I thought. Compared to what I'm doing now, 44 seems pretty good.

Its always nice to get your baseline, so you can see what is what in an actual situation.

I'm sure you're right, that underinflating tires and driving faster would give me another perspective. 72 mph with cruise control on my wife's previous cars (2003 Ford Focus and 2000 Hyundai Elantra ATs) got about 26 mpg, and 62 mph CC got about 30-32 mpg. This current car doesn't seem to suffer as much cruising at faster speeds.

Almost nothing helps to improve mileage with the 2006 Elantra. See the following tests. only a 30-45 mph P&G gives an improvement over steady speed cruise control, and it's only a 5% improvement.
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8.5 mile roundtrip country road route, temperature about 50ºF, 10 mph north wind, dry. Accelerate from stop, drive route, coast to turnaround, drive back, coast to stop. 2006 Hyundai Elantra AT
40 mph cruise control = 37.0 mpg
30 mph Cc = 35.1 mpg
50 mph Cc = 35.0 mpg
25-40 mph P&G = 37.9 MPG (2200 rpm max, LOD 60-65%, trying to avoid downshift from top gear lockup)
25-40 mph P&G = 36.6 MPG (2300-2800 rpm, LOD to 72%, encouraging 3rd gear downshift)
30-45 mph P&G = 38.9 MPG (keeping rpms <2200 rpm)

7 mile one way freeway route, same climatic conditions as above. Accelerate to 55 mph, reset trip FE meter, then enter driving routine. Note ending FE 1/4 mile before exiting freeway.
Southbound 55 mph Cc = 38.3 mpg
Northbound 55 mph Cc = 39.0 mpg
Southbound 52-62 mph P&G = 38.4 mpg
Northbound 52-62 mph P&G = 38.0 mpg
Southbound DWL 55 mph = 39.0 mpg
Northbound DWL 55 mph = 38.2 mpg
Southbound 65 mph Cc = 34.3 mpg
Northbound 65 mph Cc = 35.0 mpg
Southbound 72 mph Cc = 31.0 mpg

Net results. P&G with 30-45 mph delta beats cruise control by about 5% on country roads. 25-40 mph delta beats Cc by a lesser margin. On freeways, I might as well just leave it on Cc . Neither DWL nor P&G beats Cc at freeway speeds. Top speed of 55 mph is the sweet spot.

It could be that from an engineering standpoint, you are just pushing the Elantra as far as it will go from a FE standpoint. Some cars just do better, some are worse. Anyone who's ever tried to get stellar numbers from a Mazda product would probably agree. I did some looking around on elantra forums and you are whomping most of their numbers for sure. Most elantra drivers - even the ones with earlier generations find themselves in the low 30s or high 20s. One would think with the car's size and relatively small motor that the FE would be better, but maybe the transmission is just dumb.

I think it's the way that Hyundai geared the Elantra. I'd get great mileage if I never had to stop or start ;). Steady state cruise (with cruise control) on I95 from Virgina to NC netted about 43 MPG. Just trying to get above 33-35 MPG on around town stop and go is really, really tough. Even being gentle on the throttle and keeping TPS under 14 (default is 5) still plows through gas pretty quick. Heck, look at the EPA tests... didn't they rate it for 20 or 22 city mileage?

Oh, and as a comparison, my typical mileage in Northeast PA was about 24 or 26 MPG. That was driving like I stole it most of the time though. I'm not sure where it'd be now, but I'd take more advantage of the hills and let gravity assist versus the way I used to drive.

You're doing amazingly well. We had a 2000 Elantra, and the newer one is much larger and heavier. My listed mileage in the 2006 is based on three long 400 mile drives. Yours is based on real-world driving.

Yeah, but. I'm thinking at this point that the new Elantra is not high on my list of vehicles to replace the current Elantra when the time comes. Right now, tops on the list is either a Civic, or a Yaris... dependent upon whichever I can afford when the Elantra goes on into that dark night of existence.

Well, time for an update. I did a lot of driving this Summer in my (new for me) Scion, and didn't take the wife's Elantra out at all for a full tank drive, until this past weekend.

Last weekend, I drive it from the Bay Area to Las Vegas and back, averaging 41.85 mpg over 571 miles to Las Vegas, and 40.31 mpg on the 471 miles back to Santa Nella in the Central Valley. I could have done better, but 13 miles of Las Vegas city driving at 17 mpg drank up almost a gallon, penalizing the entire tank for the return trip.

Still, I met my goal, averaging about 41 mpg for over 1000 miles in the Elantra. That's as well as I did in a rental AT Yaris for three tanks in New England last Summer.

FWIW, I took my MT Sentra SE-R down to San Diego and back last weekend, and got worse mileage with it! 1205 miles at 38.73 mpg.

Forgot to mention I had 30 mph headwinds for about 100 miles on the return trip in the Elantra.

This is late, but thanks tons for your 02/21/2009 post.
That is very valuable data for me as an Elantra 4AT driver, even though we've got a minor weight difference.
Your numbers basically jibe with my spring/summer/fall numbers, although my Cleveland Winter hwy MPG is probably 20% off of peak due to warm-up losses.

What's the lowest you can go without having the TC unlock in 4th?

I just came back from a 1000 mile holiday trip to San Diego in my wife's AT Elantra. Using high speed P&G, I got 40.8 mpg on the first tank from the Bay Area to Oxnard, and 41.1 mpg on the second tank from Oxnard to San Diego and back to Oxnard. That's pretty good for Winter temperatures, and driving a lot in the dark and with wipers and lights on in the rain.

Tom, I just saw your question. Fourth gear TC lockup was at about 32-34 mph, I think. I didn't test it specifically, as my P&G deltas were typically 45-60 mph.

I drove the Elantra to lunch today. We were running late, and leading a friend who had to depart early, so I took the freeway, and drove the speed limit (65 mph). I got 30.8 mpg. On the way back, I did some low speed top gear P&G to see where top gear TC lockup occurred, and to see how much better fuel economy would be. The answers: 32-34 mph is only partially true. I could see TC lockup at 35 mph, and hold it down to 32 mph pretty consistently. It even held down to 28 mph once, but at those lower speeds it had a tendency to slip pretty easily. At 35 mph, I could hold it even up some pretty good hills, so 35 mph is the answer.

Second answer: I only got 33.5 mpg on the return trip, taking twice as long for the drive. I'm sure not going to convince my wife that hypermiling is useful with such a miniscule improvement. I hate ATs!

I hate ATs!

I think I've said that once or twice in my life. ;)

I repeat it for 1.5-2 hrs, twice daily. :D

I tested the AT Elantra again, to and from a class at our medical center about 20 miles away, in the dark with lights on both ways. I went 55 mph on the freeway and averaged 32.3 mpg DWL. On the way back, I drove 35 mph DWL, and averaged just 33.6 mpg.

I know it's been a while, but congrats again on busting through that 40 mpg wall... now if I could only do it with my Spectra (the Elantra's brother) with a 5 speed (no excuses, right?) more consistently, I'd be real happy! :-P

Well, I only record the Elantra's mpg on long trips, so my numbers are artificially inflated. Still, you should be ashamed of your poor fuel economy with a manual Spectra ;). Seriously, you know your potential with a manual transmission is about 170% of EPA. Whether you get it depends on how hard you try for it.

Yeah, my mild excuse is that I seem to live in a valley of Tallahassee, every road to get somewhere near my house is uphill, so I'm tackling it cold every time. And I'll admit, I've gotten slightly lazy and rusty. Being a vollie firefighter takes a toll since MPG's usually aren't on my mind on the 8 mile sprint to the station/call.

I'm trying harder now though since that is on the backburner until I finish my degree . :p

Brandon,

I was a volunteer fireman in northern Colorado nearly 40 years ago. Thanks for your service to the community.

But uphills in Florida? I don't think so.

Believe it or not, there are definitely hills here... they may not compare to those across the mountainous parts of the country... compared to the rest of Florida, these are hills! :p

I have no excuse though... :o

There are some fairly good hills in the central Florida area where I grew up.

You simply reached the point of diminishing returns. It happens to everybody.

True. At least the wall is on the north side of 40 mpg. After doing the testing, I've determined the AT Elantra is useful for long highway trips. Its highway mpg beats my Sentra, and nearly equals my xB, with a more comfortable ride and a lot less work.