My car is a 2000 accent 2 dr, manual with the 1.5litre. when i bought the car at 60000 miles, it was getting 36mpg at best, then about 33. as of recently, ive seen 30, then 27mpg, now im down to 23mpg!!! this is like V6 mileage without the performance!! a year ago, at just over 80000 miles, the timing belt went, so i had that fixed and had to have a valve job done too. the car seemed to run fine after that, but the performance is getting worse and worse, the car drags **** so much when i try to get up on it. i have NOT changed my driving habits, i am typically heavy on the pedal, but thats been how ive driven the car since i bought it. and i have accounted for using the A/C regularly. this shouldnt make a difference, i used to get the mileage i listed above while using A/C. the other problem that ive encountered is that the oil has to be re-topped off every two weeks. i dont know where its disapearing to....theres no leaks under the bottom, and it doesnt blow smoke, so i have no idea what is causing that one either.

So, ive done the following, changed the air filter many times, change the oil regularly, did the spark plugs and wires recently, just changed the fuel filter today (noticed NO difference at all), tried the Seafoam engine cleaning agent, and i keep the tires inflated to the correct pressure. i can not figure out what i should do, or, what is causing this! im getting frustrated with this car! can anyone please give me some ideas on what the problem may be, and perhaps how to fix it! thanks alot!

If you can't find a leak on the parts or on the ground the oil is either getting burned up in the engine or maybe leaking into other fluids (like your coolant).

The first thing that comes to mind: Coupled with poor mileage, your valve stem seals may be bad, letting oil into the cylinder. With your previous timing belt problem, the amount of valve damage may not have been completely realized or there may have been something wrong with the work that was done. Consider running a compression test on all of your cylinders and see if that tells you anything.

If you have poor compression in adjacent cylinders along with oil in your coolant you may have a blown headgasket.

have you changed your pcv valve?
try having it scanned, you might have lazy oxygen sensor or plugged up converter...

i have considered that they did a shabby job fixing it....i think that they may have the timing off slightly, bc i get a LOT of engine knock. trouble is tho, they only waranteed their work for 3000 miles, and ive passed that. but, thank you tho for the advice!

no, havent considered the pcv valve....thought about the ignition coils, but heard that they typically are still good on these cars well beyond 100k miles. i only have 90k on it. what do you think about that???? i have an OBD II device i can plug into it, havent tried it in a while, maybe i should check it again i guess.

you said it,

you push the car too hard, these need to be handled carefully and let them gradually get up to rpm's and speed.

i beat mine up and it slowly gets worse and worse.

when my first car was an elantra i drove it so slow and careful it drove well to the 150000 mark when it died.