New Car Mileage

My car is 5 weeks old and I’m getting 14 city/18 hwy mpg opposed to the 22/35 listed for this car. Service dept says I have to drive it 10,000 miles before that mileage kicks in. Every car person I’ve talked to says that total b.s. HELP!

I want to add that the car is a 2011 Hyundai Sonata Ltd.

Don’t Panic Yet. How Are You Reading City And Highway MPG ? Are You Use An Onboard MPG Meter ?

Do this. Drive several tanks of gas through the car. Record beginning and ending mileage and subtract to get exact miles driven for each tank and for each tank divide those miles by the number of gallons required for each fill-up. That’s your real MPG.

It will be somewhat lower in cold weather and lower yet with the more ethanol in the gas.

How far are your highway trips on average ?


A new engine will not get maximum fuel efficiency. Also cold weather, 10% ethanol fuel and driving habits will effect mileage. Short trips also decrease efficiency because your car is running cold more of the time and a cold engine runs more rich (uses more fuel). Also make sure your tires are properly inflated according to the owners manual or the numbers printed on a sticker in the drivers door jam.

X, Good Reply And Let’s Not Forget Fuel Wasted Warming The Car In Winter Weather.


I’m doing that now.

I live in San Francisco where the temperature is not East Coast cold. My previous car, 1999 Camry got better miles right from the beginning.

I really can’t see how driving 10,000 miles is going to improve the overall mileage. Is it possible this particular car is a “lemon”?

Do You Know The Percentage Of Ethanol In That California Blend Gasoline ?

I can’t imagine a car that would be “lemon” enough to have a drastic MPG deficit without some very noticeable drivability problems (CHECK ENGINE light, rough running, hard starting, poor acceleration, etcetera) or a noticeable gasoline smell when in or near the car.

Do you buy gas at the same place each time ? Try another place and see if it’s any better. Get the lowest amount of ethanol blended into the gas that you can.

Have you taken any extended road trips where you can fill up, drive for a few hours, and fill up, again ?


If you’re driving mostly in San Francisco, the mileage you’re getting is probably the best you will do.

But if you’re driving mostly on the freeway away from heavy traffic and not speeding or driving erratically, your mileage doesn’t sound very good.

btw - I looked up your vehicle here and it says it should get 26 mpg.

Keep in mind that the mpg estimate is for driving under ideal conditions, which you do not have in San Francisco and/or the SF Bay Area during most week days.

I agree that driving within SF as I do is not going to get 26mpg. However, it surely has to be better than 14. My '99 Camry got 20. On the freeway I’m getting 18 doing a steady 65-70 mph - that’s about 14 mpg less than I should be getting.

No one has yet been able to find a fix for this problem. I’m wondering if I should write to Hyunday USA and let them know about it - maybe they’ll come up with something.

None of the above drivability problems apply - acceleration is great, rides beautifully, no lights on, gas smell, etc.

I get gas at different places - usually regular unleaded.

Haven’t taken any extended road trips (only have it 5 weeks!) yet; the farthest I’ve driven from the city is about 100 miles round trip. Most driving is in town.

Good suggestions - wish there was something specific I could pin point.

Did that and it still comes to 16 mpg combined (city/hwy).

Definitely something wrong. Over on, owners are raving about the gas mileage they’re getting in this car. One quote, for example:

“Sonata GLS 6A is over 7 months old now with over 15,000 miles. Never had below 30 mpg per tank, mid to high 30s on long trips.”

Look online to see if you can find other new owners with the same problem. They may have some insight. Also check to see if Hyundai has issued a TSB (Tech Service Bulletin). You may have a faulty coolant temp sensor that makes the fuel/air mixture too rich, thus wasting gas. That would be my first guess. Second guess would be one or more “lazy” oxygen sensors that are causing the fuel/air mixture to be rich also, but aren’t quite defective enough to set off your “check engine” light.

Your fuel economy will improve after 2,000 miles and be about right by 3,000. Everything in the drive train is new and takes time to loosen up. You’re loosening the engine, transmission, CV joints, bearings, alternator, power steering pump, water pump and probably the AC compressor. Maybe even the turn signal fluid has to flow a bit.

All the factual stuff is tight and so are the belts. You also may be fighting the cold. My Yaris can maintain highway speed a lot better at 10,000 miles than it did at 1,000. It’s easier to tolerate on the highway now. I hated it then. Too much pedal action then.

So keep on driving. You should get better highway economy but you may not get 35 highway with a fully loaded car, meaning automatic transmission, air conditioning and other power using options. The fuel economy may not be for that specific model either.

One of the key phrases you used was “acceleration is great”. If you are regularly using that great acceleration you have to realize the car isn’t driven like that on the EPA test.Some cars with great power will put up great mileage numbers but they have to be driven like they have 1/2 that power.
Drive soothe and gradual, use the cruise control if you can, try to avoid stopping, if you have a red light ahead,try to get there when it is green. If you get good at doing this you can beat the EPA mileage and it is much easier on your car,

City driving, hilly conditions, and the left foot could easily contribute to mileage this low.

The line you were fed by the service dept. is total bunk of course. At the service desk you’re conversing with a service writer. Very very few of these people have much mechanical ability or knowledge so the customer often hears things that are not correct.

Try keeping the rpms under 2500 for the next week or two when driving around, and see how the gas mileage responds.

Since its a Direct Fuel Injection engine, it has the ability to run both very lean, and very rich, providing great fuel mileage, or crap fuel mileage.

I would assume that you’re enjoying the power of the engine in comparison to what you used to have with your Camry, and that’s bringing gas mileage down. Also, it takes a bit of time for the transmission computer to determine your driving patterns in order to chose the appropriate shifting points for your driving style.

Anyway, keep the rpms low, and see if that gets the fuel mileage up higher.
If it doesn’t, pull the spark plugs, and see if they are looking clean, or if they are fouled.


It’s hard to believe that a new car is getting that poor of mileage, regardless of whether you occasionally get on the gas. I get better mileage than that with my V8, and I like to floor it often.

If the mileage doesn’t improve in a couple thousand miles, make sure you document all the odometer readings and keep your gas receipts for the number of gallons, then take it back for warranty service.

Does your vehicle require high test fuel and you are useing reg.

I am curious if this has changed with time. I have the same vehicle and found this post out of my mileage concerns. I drive mostly highway miles (sales) put on 35K+ annually and have always exceeded EPA numbers on my vehicles. I am seeing numbers that vary from 28-32 mpg highway with 1700 miles now on the car, babying it from every aspect. Real numbers on gallons at fill has yet to put me above 29 MPG. Trying to find out if there is hope of seeing real improvement in time or if there may be something that needs work on the vehicle. Got this as a replacement to my civic which had EPA numbers of 34 HWY which i consistantly averaged 37-38 MPG on a fill.

You always get your best mileage after 10-20K but I’ve never gotten more that a couple more MPG. It appears that something is wrong and they need to get the computer on there to check the operation of the O2 sensors, engine temp sensor, etc. Try out a similar demo or rental unit and try that on a comparable highway run to compare. That said, EPA figures are only good for comparing one model to the next to provide a relative mileage comparison, not what you’ll actually get, and they changed the formula too.

If you do run a comparison with a similar model and you are way off, driving the same distance using the same gas station etc., you do have a warranty claim or an emissions claim.