Measuring My Kia Optima Hybrid MPGs

I recently leased a 2012 Kia Optima Hybrid.  I’ve been doing a lot of driving for work lately, so I decided to get a mid-size car that could handle a lot of highway miles plus give me decent MPGs.

Being the numbers nerd that I am, I’ve been keeping track of various different stats.

The EPA estimates for the car when I bought it were 40 Highway & 35 City for an average of 37.

After the first nine fill-ups, I’ve been disappointed.  I was averaging 29.9 MPGs, WAY below the EPA estimates.

Here’s a graph showing the numbers through the first nine fill-ups:

My numbers are extremely off.  Why is this?  There are a few options:

  • The brand of car doesn’t actually give the MPGs promised
  • My specific car doesn’t actually give the MPGs promised
  • I’m a terrible driver who drives inefficiently
  • The gallons being dispensed at the pump are not the gallons actually being put into the car

Let’s examine each of these:

 “The brand of car doesn’t actually give the MPGs promised.”

Right after leasing the car, Kia (and parent company Hyundai) was docked by the EPA for overstating their MPG numbers.  The new estimates were 39 Highway and 34 City, for an average of 36.  Kia is trying to make it right, though, through partial reimbursements that you can read about here.

Even with the “new” estimates, however, I’m still way off the mark.

How do I compare with other Kia Optima Hybrid owners?  My co-worked showed me an amazing site called Fuelly, which is essentially a fuel stat-tracking website.  The added value of the website, however, is that you can look at all other owners of the same model and see how you compare to them.

Here’s the link to the list of other 2012 Kia Optima Hybrid owners.

Here’s some basic statistical data about the Optima, as of December 20, 2012:

MPG City: 34
MPG Highway: 39
Mean: 34
Median: 33
Mode: 30
Range: 20
Standard Deviation: 4.91

The mean is right at the MPG City number, and the median and mode are to the left of that.

For comparison’s sake, here’s a screenshot and some basic statistical data about the 2012 Toyota Prius from December 20, 2012.

MPG City: 51
MPG Highway: 48
Mean: 49.04
Median: 49
Mode: 49
Range: 20
Standard Deviation: 4.41

The mean, median, and mode all fall within the EPA estimates.

Perhaps my sample size is too small?  My personal number of 30 MPGs is -.81 Standard Deviations off the mean, so perhaps it means that problem is multi-faceted: The MPGs for the brand are not what was promised, AND there are problems with my particular car.  Let’s examine the second half of that point next.

“My specific car doesn’t actually give the MPGs promised” and “I’m a terrible driver who drives inefficiently”

According to my rough statistics, I’m -.81 Standard Deviations off the mean.  So, what’s wrong with my particular car?  Is it a problem with the car or with the driver?  Or both?

In regards to the car, it’s a brand-new lease, so I would hope that there is nothing wrong with it.  After the latest fill-up, I decided to check the tire pressure.  The tires are meant to have 44 psi, but each tire was hovering between 30 to 34.  Yikes!  I’ll have to see if this gives me an improvement.

Looking at various sites about getting better fuel efficient driving, I stumbled up this post specifically about the Kia Optima Hybrid, including this video about “best practices”.

So perhaps the problem is my individual car (which I will have to continue investigating), but perhaps the problem is my driving?  I feel that I’ve tried to adjust to the hybrid, but perhaps I can I still do better?

Instead of a tachometer, the Optima Hybrid has an “efficiency” gauge that gives instant feedback of “good”, “medium”, and “poor” driving.  There’s even an “Eco Score” that gives you points for driving “efficiently”.  I throw that in quotes because it’s based on what the car thinks is ideal, but from a gamification point-of-view it creates an incentive for me to try to drive better to earn virtual “points”, which should (in theory) correspond with better MPGs.  I didn’t start tracking my Eco Points until my 7th fuel-up, and in a future post I’ll see if there’s a relationship between tank MPG and Eco Points.

[Image from CNET.]

Another potentially contributing factor would be where I live and the current weather.  I’m doing a lot of travel between Pennsylvania and New Jersey, and it involves a lot of up and down through rolling hills.  We’re also moving into winter, and as a result the car is very cold in the morning and has frost, meaning I need to burn fuel to defrost and to heat the car up when I start driving.  Will other seasons be better for my MPGs?

“The gallons being dispensed at the pump are not the gallons actually being put into the car”

The last thing we’ll look at today is about the trust you have at the pump about the gallons that you purchased.  At the end of November, I had two fuel-ups at the same station in New Jersey where my MPGs seemed really low compared to the average.  When I fueled up the second time there, the tank was about 1/6 full but I noticed that they dispensed nearly a full tank’s worth of fuel.  Something seemed off here.

Fortunately there are consumer-protection groups such as local Weights and Measures departments.  I placed a call and they’re investigating, so we’ll see if I was dealing with a crooked gas station, or perhaps my far really did take a full tank of fuel.

From an overall point of view for MPGs, since it’s a ratio of miles divided by gallons, you have to assume that the gallons being dispensed at the pump are the actual gallons being put into your tank.  If not, any calculation you do will be suspect.


So what’s next?  I see a few actions:

  • Take my car back to the dealer for a check-up
  • Try to drive my car with more efficiency in mind
  • Post pictures of graphs to a new Tumblr site
  • Post fuel updates to my Fuelly account
  • Keep making graphs, because graphs are cool

Got any tips for fuel-efficient driving?  Leave them in the comments!