Originally Posted by KoupEsEcks
Well I know that overfilling could actually have negative effects, that's why I only did it once. But I never let the gas run down all the way. I have no idea why I'm getting such mad mileage, I don't leadfoot. I hardly even depress the pedal. Last time I filled, it said I put in about 11 gallons, but it sure didn't feel like it, because I pressed the TRIP button to see how many miles to empty, and once again it said 192. As I began driving, not even a couple minutes went by before the number started gradually dropping. And it always does that. I don't understand why. I have a Magnaflow muffler and an intake in the car, BUT that couldn't even really be it, because even before I put those things in the gas mileage was still acting up. I've never gotten anything even remotely close to 300 miles out of a tank. The TRIP claims I'm getting anywhere from 16 to 26 MPG everyday, and it literally fluctuates like it's nothing. I'm thinking this is a deeper problem.
By the way, it's a 2.4 SX, and I've LONG since stopped driving tiptronic.
I'm wondering if you have a computer problem of some kind where it is running in "limp" mode or something like that. I'm not wild about these modifications you did to your car. You will have a problem with getting this fixed under warranty should you press the issue. If it were up to me I would put the stock components in place and then lean on KIA to hook up their computer to see what kind of codes it spits out.
I can post every mpg figure I have had since I purchased my car last November and I get an average of 25.2 mpg, which is somewhat surprising in that I got 26.2 mpg in my 2009 Sonata with the same engine and five speed automatic and was about 350 pounds heavier. It is possible I had more highway mileage figured in, however. With my 2008 Sonata, same engine, I got almost the same fuel mileage. Oddly enough I think the automatic actually gets better fuel mileage. The new six speed transmission is supposed to yield 8% more fuel economy than the previous 5 speed. But I haven't seen it yet.
I'm thinking of working up a fuel mileage spreadsheet sometime to use in Excel or OpenOrg if I can't find one already done somewhere on the internet. This makes it doubly accurate. I'm always dubious about claims of fuel mileage of those who claim certain numbers which seem outlandish. I'm not saying that of you but sometimes people tell me numbers which I know to be ridiculous. And they always use one tank of gasoline and don't keep good records. I do and always have.
I would suggest you start keeping meticulous records beginning today and see exactly what you are getting. You need reliable numbers to show the dealer.
BTW, have you changed the tires, wheels or tire diameter? (wider tires yields less fuel economy)
I just wish people would leave these vehicles alone. Sometimes they are their own worst enemy. (I'm not speaking of you but when I see some of these big or small after market, and very expensive, wheels on cars I just think these people were born with only half a brain. They put thousands of dollars in wheels on these $2 cars.)