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Gasoline Grade

Rat Fink

New Member
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City
Alpharetta
State
GA
Country
United States
What I Drive
2007 Lexus RX350
#1
According to the owners manual for a 2018 Stinger GT it is OK to use 87 octane fuel in your car. It further recommends using Top Tier gasoline which has the detergent mix that Kia likes. I live in the Atlanta, GA area and Costco sells Top Tier gasoline in 87 and 93 octane. My GT2 runs fine on 87 octane as well as the 93 octane. My understanding of octane rating is that 87 and 93 octane have the same energy potential. The 93 octane just resists preignition better than 87 octane. The 93 octane gas allows the computer to give the engine more spark advance ( since 93 octane resists preignition) and that is the reason you can make more power than with the 87 octane gas. The 93 isn’t more powerful, it just resists preignition better. So if you run 87 octane in you vehicle, place more demand for power on your engine (I.e. floor it) your computer will start to advance the timing. When/if the knock sensor detects preignition, the computer responds by pulling timing to resist the knock (preignition). That is where you lose power compared to 93 octane gas. Not that 87 has less energy potential, it just doesn’t resist preignition to the same level. My impression from what I think I know about cars and what Kia relates in its manual is that you can run 87 Octane as much as you want, you just won’t make the higher levels of power 93 octane will due to 87 being less resistant to preignition. So, am I missing something? There are times when I want to save some on gas expense and times I want to make the most power. Thanks in advance and be kind, this is my first post. :)
 

TurboTx

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573
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192
State
CO
Country
United States
#2
In my experience it doesn't seem to make much difference either way. When gas spiked I went down to 87 for the first time in years because I mentally couldn't make myself pay that much for premium. I honestly couldn't tell a difference, it idled about the same and overall mileage was about the same. I'm sure it was probably slower, especially with the jb4 disconnected, but I started taking it easy on the throttle anyway.

So long story short, you can try 87 to save a few bucks without sacrificing much. I would try a tank of each to see which feels better to you. 👍
 

Volfy

New Member
Messages
6
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1
City
Missouri City
State
TX
Country
United States
What I Drive
2019 Kia Stinger
#3
It all depends on how the car is driven and what the prevailing conditions are. It is one thing taking a lightly loaded car on an easy solo cruise over a flat fwy in mile-high Denver on a cold November day. It's quite another to be smashing the throttle wide open in a car heavily loaded with passenger/luggage, going up a steep hill, in 105F Summer heat near sea level.

If the peak cylinder pressure is nowhere near high enough to cause impending knock with 87 octane, then pumping 93 is just a waste of money. Consider what you might put your engine through that particular tank for fuel, then fill up accordingly.

Conversely, be mindful of what the AKI/Octane is in your fuel tank... and drive accordingly.

Now then... that is for stock ECU and no engine mods. If you start adding things like JB4, then your particular map/tune will dictate your octane requirement.
 


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