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Discussion Starter · #1 ·
So I bought a 2012 Hyundai Sonata SE Turbo almost two years ago this April. I was impressed by the fuel economy and the handling. But since this past summer, I've been steadily getting worse and worse fuel efficiency.

I drive on the highway quite a bit, but I'm not even getting close to 30 MPG. A majority of the time I'm getting closer to 26-28 MPG on the highway and that's with Eco Boost and cruise control on. For instance, last night I was picking up a friend at the airport. It was 100% highway driving on a full tank of gas and I was barely getting 28 MPG. When I'm driving around town? I get roughly 17-19 MPG. To be honest, I don't drive around town a lot.

The fuel economy is frustratingly and unacceptably low and it's costing me a lot of money. I've got roughly 36,000 miles on the car and I try to keep her in good shape. In an attempt to eliminate variables I've recently replaced all the filters, got brand new tires, and had my oil changed. But I'm still getting the same numbers.

I'm not a big car guy, but I expect better performance than this from my Sonata. Other than taking it to the dealer and having them take a look at it, what else can I do?
 

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So I bought a 2012 Hyundai Sonata SE Turbo almost two years ago this April. A majority of the time I'm getting closer to 26-28 MPG on the highway

The fuel economy is frustratingly and unacceptably low and it's costing me a lot of money...... In an attempt to eliminate variables I've recently replaced all the filters, got brand new tires, and had my oil changed. what else can I do?
You never mentioned a loss in power, so I assume your engine is running well.

I assume last winter your mpg went down, but not like it is now? I also assume that after last winter's low mpg, your mpg got better, till this major downward mpg plummet? Is that correct? I averaged 39+mpg from May to December 2013. However, mpg has dropped to the 38mpg level during this winter.

Might you be driving in the city more than in the past? That WILL decrease mpg, of course. Are you driving further, which may cause you to drive faster, & getting less mpg?

When you changed the tires, did you put bigger tires on? Bigger tires, specially with bigger diameter wheels can collapse your mpg. New tires that aren't LRR tires can decrease mpg, too. Keep your tire pressures up. I routinely run higher than 35psi. Of course, reduce tire pressures during snow or heavy rains.

Altho Pennsylvania has increased stations selling 100% (ethanol-free) gasoline, there still are no stations in Pittsburgh.... a few stations, 20-30(?) miles from Pittsburgh.
 

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Winter blend gas causes lower MPG's.
 

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For some reason, I noticed my MPG increased after about a 500-mile round-trip road trip. Also, I just feather the gas to maintain speed on the highway.
 

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I rented a 2012 GLS 2.4 Liter and put almost 1,500 miles on it in less than a week the average gas mileage was just over 32mpg, most of the miles were interstate. My 2013 Sonata 2.0T SE has not hit 30mpg yet with interstate driving. I just like the seat of the pants feel when 18 PSI of boost spools up. Gas mileage takes a back seat to performance.
 

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I'm not a big car guy, but I expect better performance than this from my Sonata. Other than taking it to the dealer and having them take a look at it, what else can I do?

I would guess the intercooler, intake manifold and valves are getting full of oil and gunk.

Do you ever drive it hard through the gears and to redline?

Also have you ever had the plugs out and looked at them? The Gen Coupe 2Ls come with the plugs gapped way to tight. But do not go to the factory spec.

What I found is the plugs gapped at .028, factory spec is .044, but it runs best at .036. Stay with the OEM plugs too.
 

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Ninety-three octane 10% ethanol city/stop n go rural two lane & me foot in its arse comes to about 25-26 mpg.

Steady 75 mph is the low 30s.
 

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No mater what I do highway or city, everything has been changed concerning filters, plugs, oil... i never see over 20 mpg even when i drive like an old granny. I have complained to my dealer about it, they say its normal for the winter. Being I am in WNY and got the Car 10/26/13 i have not had a chance to drive it in warm weather at all so i pray it getys better come spring.
 

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I had a 2011 2.4 for 3 years had the Borla cat back and straight pipe the midpipe so I had no secondary cat and I had a k&n intake I was getting 28-32MPG and that was me slamming on the gas every day and every moment now in my 2012 sonata 2.0T where I have a Borla cat back and injen intake I'm getting 20MPG on a good day and I drive extremely normal nothing crazy anymore .....
 

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1) What tires did you put on

2) Are you letting the car warm up before driving and if so how long is is idling?

3) How are you calculating? using the built in or distance/fuel equation

4) Do you haul lots of stuff around in your car

5) Have you noticed if your car is hanging in a lower gear for an abnormally long period of time?
 

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My 2012 SE 2.0T has 40K on it now. Highway driving, I can routinely get 35-37 mpg. City/combined driving about 26 mpg. I still use 87 octane.
 

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Discussion Starter · #13 ·
Sorry everyone, grad school has been eating up my life. I haven't had much time to come and post on here.

You never mentioned a loss in power, so I assume your engine is running well.

I assume last winter your mpg went down, but not like it is now? I also assume that after last winter's low mpg, your mpg got better, till this major downward mpg plummet? Is that correct? I averaged 39+mpg from May to December 2013. However, mpg has dropped to the 38mpg level during this winter.

Might you be driving in the city more than in the past? That WILL decrease mpg, of course. Are you driving further, which may cause you to drive faster, & getting less mpg?

When you changed the tires, did you put bigger tires on? Bigger tires, specially with bigger diameter wheels can collapse your mpg. New tires that aren't LRR tires can decrease mpg, too. Keep your tire pressures up. I routinely run higher than 35psi. Of course, reduce tire pressures during snow or heavy rains.

Altho Pennsylvania has increased stations selling 100% (ethanol-free) gasoline, there still are no stations in Pittsburgh.... a few stations, 20-30(?) miles from Pittsburgh.

MY MPG last winter went down but not this drastically.

I'm drive on the highway more than anything.

My trips have been about the same distance actually so there's no change there.

The new tires I put on are exactly the same size and I've kept the pressure around 35-36.
 

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Discussion Starter · #14 ·
1) What tires did you put on

2) Are you letting the car warm up before driving and if so how long is is idling?

3) How are you calculating? using the built in or distance/fuel equation

4) Do you haul lots of stuff around in your car

5) Have you noticed if your car is hanging in a lower gear for an abnormally long period of time?

1) I put on Nexen tires, I can't remember the specifics but they're the same size as the ones I originally had the vehicle. There has been no change performance wise between my old tires and these new ones.

2) I don't let the car idle long at all.

3) I've been using the built in distance and keeping a log of how many MPG's I actually get every fuel up.

4) I don't

5) I haven't really noticed that at all actually.
 

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Discussion Starter · #15 · (Edited)
Just to give everyone an update, I did take the car back to the dealership and they said that there was nothing wrong with it. I don't believe I'm getting the run around but I can't be sure.

Any suggestions?

By the way, thanks for your help everyone. I really appreciate it :)
 

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Kind of stumped. The only thing I can really think of would be the transmission mapping. It does learn driving styles like most transmissions do nowadays. Perhaps disconnecting the battery for 30 minutes and reattaching will help since it should clear the learned behaviors and reset to default. The other way is to hook up to the OBD and reset there.
 

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I have a 2013 2.0t Limited and I'm getting about 20mpg average with 93oct gas and I live in the burbs. My commute to work is 4 miles highway and 4 miles suburb driving. I don't drive hard but I don't use ECO either. In the summer when I used ECO, I was only getting 24mpg with 87oct gas so it wasn't that much better. I don't ever remember ave more than 25mpg in that I have had the car.
 

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Maybe your brakes are dragging slightly. Believe me, it doesn't take much of a drag to bring down the fuel economy. My new 2013 Elantra had brake drag and the MPG dropped 4 MPG! Since it was only 7 months old the dealer lubed the brake slides/pad ears and the MPG's went back up. With the design of the brake caliper, clean/lubing the brakes will be a yearly deal if you live in the salt belt.
 

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My first fuel-up since buying my 2011 about a month ago, I only got 17MPG. I primarily drive in "town" conditions (I live just outside a VERY small city, my 5 mile commute takes me about 12 minutes to get home). I was really hoping for better gas mileage as my last vehicle was a pig (it was a 2005 Santa Fe AWD and only got about 12-14 MPG.
 
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