Picked up the 2011 ET on 10/4. Have about 700 miles on it, mixed driving with most of it city and counrty roads. Cumulative MPG per trip computer is 30.4 and has been climbing. I an very pleased with the car thus far.

 

Purchased our ET on June 1st, 2010 and have just turned 16,000 miles. I had consistently been averaging about 32mpg highway. Recently I had a 15,000 mile service work performed consisting of pulling the battery cables and placing new felt spacers between the battery case and cables. Besides having to reset all the radio settings, due to the battery being disconnected I guess, i am now getting only 27-28 highway mpg on a trip immediately following the service. Curious if anyone else has run into this and if disconnecting the battery may have had some effect on the car's electronics.

 

Disconnecting the battery will erase your ecu's 'learned' fuel trim settings, and temporarily put you into a less efficient/richer base map mode until it relearns the optimal settings. This is why you're seeing a drop off in mileage. It will correct itself in due time.

I know a common trick for people on Elantraclub.com is to disconnect the battery prior to getting on the dyno to get higher HP readings (the base map produces a little more power, at the expense of optimal fuel consumption). Don't worry about the electronics, I've disconnected my battery many times when installing after market parts.

 

Before the temperature took a drop, I was averaging between 32 and 35 mpg highway. I can't definitively say, but I think the combination of my CAI, higher diameter/less restrictive exhaust, and lowering springs attributed to the increase in fuel efficiency.

 

Zielritter, thanks for the great reply concerning the decrease in fuel mileage. I thought i might be stretching it a bit but from your answer it does seem that disconnecting the batttery can effect gas milage for a while. I will keep an eye on it and hopefully it will improve quickly.

 

You're welcome. Keep in mind too that during the colder months the thicker air will take a toll on your mileage along with the less efficient 'winter blend' fuel that is rumored to be used by gasoline companies.

I don't know if these factors will be relevant for you, but during the winter I see a 10-12% drop in my economy.

 

Ditto for me as well on the 10% economy drop. Not only the thicker air, but the colder air also lowers fuel economy. Add to that the use of the windshield defogger (that uses the A/C) and the extra time it takes to warm up the engine and scrape the frost off the windshield also lower fuel economy.

What I've seen some people do is actually disconnect the air inlet tube that pulls colder air from the outside and redirect it to over the exhaust to pull in warmer air. They claim it helps raise fuel economy in the winter. I've never tried it.

 

I have now driven about 1200 miles since the battery was disconnnected and my mileage seems to have returned to normal. I averaged 32.1 mpg on a 120 mile trip today.

 

I purchased a brand new 2011 Elantra Touring Sport about 3 months ago. I love everything about the car so far except the fuel economy. I am not getting anywhere close to the mileage that is advertise. They claim it does 8.7 L\100 km City and 6.5 L\100 km Highway. I drive a half hour one way to work on the highway and both my house and work are within minutes of the highway. I mainly drive on the highway so I thought my fuel economy would be closer to 6.5. According to the trip computer, I am only getting 9.4 L\100 km. Way above the city mileage. I know you are going to say that I drive it too hard, I use bad gas, etc and that’s why I am getting such high numbers and I would believe you but I bought this car to replace my 10 year old 2001 Nissan Sentra and I am getting worse mileage than it. I know the Elantra Touring isn’t the most fuel efficient car in the world but according to the numbers, it was better then my old one and that was good enough for me. The 2001 Nissan Sentra numbers were 10 L\100 km City and 8 L\100 km Highway according to the reports, and I was still getting that mileage even after 10 years. I could squeeze 500 km out of my 42 L gas tank. The Elantra Touring has a bigger gas tank at 53 L and I still haven’t hit 500 km with it yet. I followed the recommended break in of the vehicle and all that and now I have over 5000 km on it. I will agree with you that many different factors depend on fuel economy but I can assure you that I drive the Elantra Touring the same way I did the Sentra, I take the same route, I stop at the same gas station, I set the cruise on the highway at 119 km/hour and my fuel economy is much worse. Is there something wrong with my car to be sucking up more gas than normal? If this appears normal, then I am upset that such a great car can’t live up to it’s fuel economy numbers. Please tell me there is something wrong with my car because I really don’t want to part with it.

 

First, the Sentra is smaller and lighter than the Touring.
Second, driving style does make a big difference.
Third, are you sure the tires are at the correct pressure?
Fourth, you can't go by the trip computer. That is an ESTIMATE not exact. You need to (1) do the mileage by hand and (2) reset the computer every time you fill up. Are you doing that?