Horrible gas millage with 2012 Kia Rio

I just got the car. I found that it went through 8.1 gallons of gas at 195 miles, so around 22.5 mpg. It should be getting around 28 in town and 46 mpg on the freeway I believe. It has higher miles.

Has anyone had experience bad gas millage with the 1.6 gdi? Are there any common problems that decrease gas mileage with this model? I’m trying to troubleshoot cheap things first.

It has new spark plugs and I cleaned the map sensor. (It seems to idle a little high till it warms up after cleaning the map sensor).

I’m on a second treatment of Lucas injector cleaner.

I’m replacing the thermostat and coolant temp sensor in the morning.

What would you all check next?

How does one test the fuel pressure on direct injection engines? I’m not finding a lot online.

Thank’s for any advice.

*The 36 mpg freeway was supposed to be 36 mpg.

What are your thoughts on aftermarket O2 sensors?

Folks on fuelly are getting around 30 mpg average, so yours is on the low side. Has a mechanic inspected it? Any dash lights on?

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No and no.

You could have a dragging brake. Drive it for a while, pull well off the road and feel if one of the wheels is hotter than the others.

195 divided by 8.1 = 24.07 so recheck your math . Your vehicle is rated up to ( key words up tp ) 29 city / 37 HWY . I would be expecting to much to get that very often .

I don’t think you have a problem . Check it the old fashioned way on a highway trip at no more than 65 MPH and see how close to 37 you get.

Short trips - stop and go city traffic all reduce the miles per gallon.


Thanks. That was supposed to be 8.81 gallons.
I’d say half the driving was in town and the other half freeway.

Then you don’t have a problem .

My guess is what you are getting is what anybody else would get with the same vehicle, same accessory usage, and same type of driving. If you had problems with the fuel pressure, the MAP sensor, or the injectors you’d be getting lean or rich diagnostic codes. Ask your mechanic to check for that. If nothing found, forget about those three as the cause. After that the most likely problem would be incorrect actual coolant temperature or incorrect sensed temperature. Beyond those, any problem, – if you have one – would probably be with the valves. If it is possible to check the valve clearances, that test is worth a shot.

I expect you already know this, but the most common cause of lower than expected mpg is the driver’s right foot – pressing too hard on the accelerator pedal during accelerations. There’s no way for manufacturer to know how quickly their customers will accelerate in typical use, and since rapid accelerations consume a lot of gasoline, no way for the manufacturer to adjust the mpg ratings for that factor.

Tire pressure, air filter, spark timing, wheel alignment, engine compression wet and dry, blow by, The above should reveal the cause of such poor fuel economy in the results being out of spec of normal.

I think your sample size is too small to form a reasonable conclusion. I’d get an average over three tanks or so, and see where you’re at before deciding that something is wrong with the car.


As long as the car is running correctly, the most important factor is your right foot.


Since it’s direct injection, check the oil level to make sure an injector isn’t dumping fuel in the oil. Not real likely, but it’s good practice to check the oil level anyway, right?

If there aren’t any check engine lights, I doubt anything is really wrong as far as sensors or operating temp. I think you’ve done well with the plugs and cleaning the MAF. I’d clean the throttle body and replace the air filter too. Then you’ve basically completed the equivalent of a modern day tune up.

George brought up the valves. I wonder if carbon coked valves (no fuel hitting them to clean them on direct injection) could cause lower fuel mileage? That’s the only thing I can think of offhand that wouldn’t necessarily set a CEL and might reduce fuel mileage, other than dragging brakes like texases mentioned.

I agree with Fodaddy, though. I’d want a larger sample size (2-3 tanks of fuel) before I decided I had an issue.

Thanks. I did do the air filter and I cleaned the throttle body.
I tested the breaks. No hot wheels.
I’ll check the oil tomorrow before I change it out.
Yeah I’m hoping Fodaddy is right. I drive like an old man so I was surprised to see my gas millage.

I forgot to mention there was quit a bit of carbon built up in the exhaust tip. Pretty sure it’s running rich.

Those GDI engines put out a fair amount of soot, so that’s could be normal.