Ridiculous Gas Mileage on 2004 Sonata AT or FUEL LEAK???

Hi Everyone!
I have a 2004 Sonata Automatic w/71000k miles. I drive very little
because I take a train to and from work but I recently noticed that my
gas mileage on the car is not low but simply ridiculous! Basically, I
reset the trip odometer at full tank and was able to drive exactly 265
miles on 1 tank instead of the average 400!!!
Upon finding this, I took the car to a mechanic to inspect for gas
leaks. He did not find any and said he is sure the car is not leaking
gas! He did not see anything obvious that would cause it to use so
much gas!
AC has not been turned on during the test. Heater only a couple of
times. Driving was normal, calm, city driving.
I REALLY NEED YOUR HELP! WHAT MECHANICAL PROBLEM WOULD CAUSE IT TO
BEHAVE LIKE THAT?
P.S. Please, please tell me specifics that could cause this and not
"take it to your local dealer", I already know I have that option =)
"pay big bucks for diagnostic only to find out I need to invest a
couple of thousand in the car". Thanks!!!

 

Understanding that you trust your mechanic....
Under-inflated tires, higher than normal lube oil level, improperly gaped
spark plugs, dirty air filter, dirty fuel injectors, short driving trip,
miss-aligned wheels, heavy items in the trunk, short driving trip in colder
weather/temperature, etc., etc., etc.......!!!
Is this used car new to you with only 71000 miles?
If yes, what were the driving habits of the last owner?
If not, and all of my specifics are in order, and you do not have any CIL, I
would suggest to disconect your battery for 10 minutes, and with the battery
disconnected, turn on the head light and then back to the off position,
re-connect your battery and take your car on the highway at 60m/h for about
60 miles without slowing down, that should/might reset the "cpu" to a new
driving habit and take car of the problem......If not, "take it to your
local dealer", You already know you have that option =).

TheIceAge05 at www.hyundai-forums.com

 

I have a 2004 Sonata Automatic w/71000k miles. Basically, I

Why are you complaining? A Sonata is a big car and an auto is going to
use a lot of petrol around town. Also the car will use more this time
of year as it has to warm up. What size engine is it; must be at least
2.0 ?
My 1.6 Lantra with manual gearbox does around 280 on a full tank and
mixed driving or 380 on a run.
I think 265 sounds about right from what you say.

 

OK, here is a specific. Your driving habits.

My last car used to give me 25 to 27 mpg consistently. I bought a new car
and my wife now uses the old one. She drives short trips around town, never
goes on the highway, never drives long enough for the car warm up to normal
operating temperature. That 25+ dipped to about 17 mpg.

Your daily trip to the train station, possibly in traffic, is murder on
mileage. Unless you were getting 400 miles under the same conditions,
nothing is wrong. Take a nice long ride on country roads where you can
cruise along non-stop at 45 mph and watch the numbers come up. Also, did
you run out of gas at 265 miles? How many gallons did you actually put in
the tank at fill up afterwards?

 

280 on a full tank for an Elantra? That's crappy. I can get 280 on
just short of half of a tank on my 08.

 

Hi! Thank you everyone for responding! I was "complaining" because,
even though I know city stop & go driving uses much more gas than
freeway driving, I didn't think it's such a HUGE difference! This car
goes around 400 miles on 1 tank (17.2gallons?) on the freeway, so if
it was 350 miles city driving I would understand, but I was able to
drive 265 miles on 1 tank...so that's~15.4 MPG. If there's anyone here
that has an '04 Sonata AT and gets the same gas mileage in stop&go
city driving, then I'll calm down =) Thanks!

 

Hi! Thank you everyone for responding! I was "complaining" because,
even though I know city stop & go driving uses much more gas than
freeway driving, I didn't think it's such a HUGE difference! This car
goes around 400 miles on 1 tank (17.2gallons?) on the freeway, so if
it was 350 miles city driving I would understand, but I was able to
drive 265 miles on 1 tank...so that's~15.4 MPG.

*********************************************************

The tank may hold 17.2 gallons, but how many did you actually put in to fill
it back up? Surely it was not 17 unless you ran it dry until the car
stopped. Let's deal with fact rather than supposition. Your actual travel
distance sounds about right for a tank getting down to about a quarter
leaving 3 to 4 gallons. If a fillup was 14 gallons you are getting closer
to 19 mpg. If it was 13 gallons you are getting 19 mpg. That is very
respectable for city traffic.

 

I would say I *almost* ran it dry this time for the purpose of testing
how many miles I can go on 1 tank. The arrow was in the red zone, on
"E".
Mike.

 

I would say I *almost* ran it dry this time for the purpose of testing
how many miles I can go on 1 tank. The arrow was in the red zone, on
"E".
Mike.

***********************************************************

Almost is not a very accurate term. I'd guess there were at least 3 gallons
left, meaning you used about 13. That translates to a very respectable 20
mpg. Pretty good under short trip driving conditions. On my Sonata, the
warning light comes on and I can go another 50 to 60 miles on what is left.

 

Ad Edwin says, look at your receipt if you have it, and determine you
actual economy. Discussions about what maybe wrong with the car and wh
fuel economy is poor are pointless without determining an actual measure
fuel economy in the first place.

And yes, city vs. highway will cause a huge variation. In my 3.0 lite
Taurus:

Highway 24-29
Mix 19-23
City 17-20

 

The way to check your fuel consumption is not to rely on the gauge, but to
fill the tank right to the top, note the mileage, drive until the tank is
nearly empty and then re-fill it to the top and note how much fuel you put
in and the new mileage. This way you will have a much better idea of how
much was actually used.

Regards
Jeff