Over consumption of fuel?

66149

MEMBER
2018 HYUNDAI ACCENT
1.6L
4 CYL
2WD
AUTOMATIC
80,000 MILES

The car burns too much fuel when the tank is full
I have a digital display fuel guage and every quarter of a tank is supposed to drive me 90 kilometres as I have noticed previously and I drive the same distance every day and at the same time to and from work. I noticed recently that the mileage per quarter of a tank is inconsistent and and almost less than half of what it should be. I recently changed the spark plugs thinking it's a torque issue but it didn't help. I would like to point out that once the tank reaches half full the mileage goes back to what it's supposed to be but as long as the tank is full it drives way less mileage

Thursday, December 4th, 2025 AT 4:42 PM

1 Reply

STEVE W.

MECHANIC
15,231 POSTS

Have you actually checked the real mileage or just going by the meter? IE Go to a station, top up the tank, record the odometer reading. Now drive the car as normal. Fill up when you have used 3/4 tank, record the odometer and amount of fuel again. Now take the total KM you drove and divide it by the amount of fuel to get the actual KM of fuel used. I have never seen one of the meters be correct. However this would let you see the real number.
Now if it is actually using extra fuel but only when over 1/2 a tank there are two options, one is that you have a leak that only shows with a full tank. Do you smell anything? Any staining or spots on the ground? If no the other option would be if you live in an area that gets cold, there are usually different fuel blends for winter over summer, the winter fuel always burns more due to the fuel and the cold temperatures.
However I would try the math option first, I've rarely seen any of the fuel use meters that are correct.

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Thursday, December 4th, 2025 AT 6:46 PM