2015 Kia Optima Gas Tank Size

The 2015 Kia Optima has a big 18.5-gallon fuel tank. Let’s learn more about your Optima and how to save money on gas.
Written by Matt Terzi
Reviewed by Jessica Barrett
The 2015 Kia Optima has an 18.5-gallon fuel tank, which is universal for both the 2-liter and 2.4-liter engine varieties and all trim levels.
Keeping your engine running smoothly means knowing not just how much fuel to put in your car, but what octane levels of fuel your car can safely use.
is here to help you understand your car’s gas tank better. 
And hey, while you’re here, why not learn how to reduce your
Kia Optima’s insurance costs
, too?
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How big is the gas tank on a 2015 Kia Optima?

Known today as the K5, the Optima has long been one of Kia’s best-selling cars and a staple of the sedan market. 
Every 2015 Kia Optima has an 18.5-gallon gas tank, regardless of whether they have the standard 2.4-liter engine or the turbocharged 2.0-liter.
Both engine types require 87 octane fuel or higher. Some cars with turbochargers need higher octane levels, but the Kia Optima gets on just fine with regular unleaded 87-octane gasoline. 
There aren’t any benefits to using octane levels higher than 87, despite what some popular myths claim.
MORE: What do the gas octane ratings actually mean?

How to check your 2015 Kia Optima’s gas tank size

Interested in seeing for yourself just how big your 2015 Kia Optima’s gas tank is? There are a few different ways to find out.

Measure the gas tank

Some people really enjoy math—and finding the volume of your 2015 Kia Optima’s gas tank the fun way simply requires calculating its volume.
Simply measure out the width, length, and height of your gas tank, then multiply those values. Now just divide the result by 231, which is how many cubic inches are in a gallon. Your final result should be 18.5.

Check your owner’s manual

The less-fun way is to simply check your car’s owner’s manual, which lists your fuel tank capacity and tells you what octane levels your engine can handle. 
Again, be sure to use 87 octane unleaded gasoline in your 2015 Kia Optima.

Drive till empty, then fill it up

And now for the more adventurous method of finding your gas tank size: driving until your Kia Optima is out of gas and then filling the tank back up again.
We don’t recommend driving until the engine sputters out, but rather driving until your fuel gauge reaches “E” and then filling up the tank fully. 
This won’t give you an exact volume—you’ll hopefully still have some fuel left in the tank when you fill up—but it’ll give you a general gas tank size range.
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How to save on fuel costs in a 2015 Kia Optima

Your 2015 Kia Optima has a fuel efficiency of around 23 MPG city and 34 MPG highway, which is slightly below average for a car from that model year.  And with gas prices being what they are these days, it’s always a good idea to try and conserve fuel whenever you can. 
Here are some useful tips to save you some money at the pump:
  • Drive conservatively, even if you have the sporty 2.0-liter turbo engine. The further you push your gas pedal, the more gasoline you’ll send flowing into the cylinders. Aggressively driving between red lights doesn’t get you to work any quicker.
  • Stay on top of vehicle maintenance to keep the engine operating smoothly. Oil and other fluid changes and keeping with annual maintenance schedules can keep the engine using optimal amounts of fuel.
  • Don’t leave your car idling for no good reason. Your Kia Optima will warm up a lot faster during the cold months by driving it than by leaving it idly running for 20 minutes. That’s just wasted fuel!

How to optimize your 2015 Kia Optima’s insurance coverage

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