Info on my '05 Elantra 2L, auto trans.
I purchased the car on Oct 27, 2005 and tomorrow it will be one year
old.  I have slightly more than 21,000 miles on it. This is my
maintenance info:
2500  miles    Dec 12, 2005 Lube, oil, gasket and filter n/c
5989  miles    Jan  16, 2006 Lube, oil, gasket and filter n/c
9554  miles    Apr  18, 2006 Lube, oil, gasket and filter n/c
13738 miles   May 31, 2006 Lube, oil, gasket and filter n/c
                     balanced and rotated all four tires $39.95
14087 miles  Jun 06, 2006  Replace defective power mirror switch
                     assembly P/N 93570-20110-as warrantee n/c
16525 miles  Aug 01, 2006  Lube, oil, gasket and filter n/c
                    Replaced defective trans solenoid PN 46313-39051
                     replaced lost ATF and anti freeze, warrantee n/c
19525 miles  Sept 29, 2006 Lube, oil, gasket and filter n/c
                    Rotated all four tires   $29.06
                    Replaced both right and left wiper  blades
                    part number 98350-2d800   $17.98
                    part number 98370-2d800   $17.98  

All work done at dealer, Oil is Pennzoil 5W30

Mileage:
City   25.+ MPG
Suburban  28.+  MPG
Freeway at @65 MPH,  33.+ MPG
High Speed @102 MPH avg 28.8 MPG

On the high speed section I drove the first 100 miles at 70 MPH and
for the next 300 miles I never went  less than 90 MPH and at times
over 115 MPH. After the first 100 miles a guy with a ton of antenna
and all kinds of stuff on his dash board blew past me.  I hooked up
with him for the next 300 miles I would let him get about a quarter
mile or more in front of me. The only time I slowed down was for
traffic. At times cars got between him and I and I would have to go
like a bat out of hell to catch him.  That's when I was going over
115+ MPH. I finally had to stop for gas as the fuel warning light was
on. The car rode rock solid, no float, no lift, no sway.  The car rode
smooth. Surprisingly the tach never went to high.  I don't remember
what the tach numbers were but I remember being surprised at how
relatively low they were for that high of a speed.

On the freeway I usually start looking for gas around 410 to 420
miles.

My oil changes are at no charge from my dealer as long as I own the
car.  Its a new dealership and I was the first car they sold.