What's the best octane to use?

[Ahawk1968]

I do think there is a limit to ethanol content in normal pump gas. 10%?

 

[MisterMac]

I do think there is a limit to ethanol content in normal pump gas. 10%?

That is correct.

 

[ecko04]

I’m not sure what the maximum limit of what our cars can handle in terms of ethanol content on the stock fueling system, but 10 gallons of pump gas with 6 gallons of E85 will yield about an E38 mixture. I’d be concerned with a drop in fuel pressure from too much of the corn juice.

 

[MisterMac]

I’m not sure what the maximum limit of what our cars can handle in terms of ethanol content on the stock fueling system, but 10 gallons of pump gas with 6 gallons of E85 will yield about an E38 mixture. I’d be concerned with a drop in fuel pressure from too much of the corn juice.

Not just that, but also the highly corrosive nature of ethanol. Our parts aren't made for that. 10% is the maximum.

 

[ecko04]

10% isn’t the maximum the fuel system can handle before maxing out the injectors.

Ethanol being corrosive is overstated and a bit misleading. Ethanol by itself is not corrosive. E98 will likely contain an average of 0.5% water.

When ethanol is mixed with sufficient amounts of water — think taking a water hose to a tank of ethanol — this can cause corrosion, but the effects can be minimized with easy steps such as keeping the fuel tank full when the vehicle is stored, simply driving the car or using stabil for long term storage.

In our case, running an E15, E20, or E30 mix will not harm any of the components of the car’s fuel system. Ethanol is not an acid, will not eat through rubber, and has little effect on aluminum fuel system components.

Totally agree with that most folks will only see <= E10 when using pump gas.

 

[MisterMac]

10% isn’t the maximum the fuel system can handle before maxing out the injectors.

Ethanol being corrosive is overstated and a bit misleading. Ethanol by itself is not corrosive. E98 will likely contain an average of 0.5% water.

When ethanol is mixed with sufficient amounts of water — think taking a water hose to a tank of ethanol — this can cause corrosion, but the effects can be minimized with easy steps such as keeping the fuel tank full when the vehicle is stored, simply driving the car or using stabil for long term storage.

In our case, running an E15, E20, or E30 mix will not harm any of the components of the car’s fuel system. Ethanol is not an acid, will not eat through rubber, and has little effect on aluminum fuel system components.

Totally agree with that most folks will only see <= E10 when using pump gas.

I have insider information from the Ethanol company a family member worked at for several years that contradicts what you say. However, it's your car and you may do as you please.

 

[ecko04]

I have insider information from the Ethanol company a family member worked at for several years that contradicts what you say. However, it's your car and you may do as you please.

Cool story.

 

[MisterMac]

Cool story.

Yeah, if only it could be shared.

The corn lobby is crazy strong.

 

[Ahawk1968]

Not just that, but also the highly corrosive nature of ethanol. Our parts aren't made for that. 10% is the maximum

Yup, I am judicious with my use of 3-4 gallons of E85 to a full tank of premium. It sure is fun.
Time will tell.

 

[MisterMac]

Yup, I am judicious with my use of 3-4 gallons of E85 to a full tank of premium. It sure is fun.
Time will tell.

Yes, I've done it twice, but didn't notice any difference

 

[TruStinger]

I have insider information from the Ethanol company a family member worked at for several years that contradicts what you say. However, it's your car and you may do as you please.

Contradicts which part? Ethanol in fuel has been around a long time and while the corrosive quality of it exists, its negated on newer cars. Ive seen people say that isnt a a problem until E35-40 territory.

 

[Mr. Tech]

Update. BJs gas is terrible. Noticed a significant loss of power compared to Shell 93. Lost .2 to .4 on my 0-60 by the time I got to the end of the tank. Back to Shell 93.

 

[Dr_jitsu]

I run 93 Octane only. Texas has lots of it. Guys spend a ton on ricer math mods but in reality higher Octane means better performance. Better fuel will give more hp than a CAI for less money.

 

[Mr. Tech]

Update. BJs gas is terrible. Noticed a significant loss of power compared to Shell 93. Lost .2 to .4 on my 0-60 by the time I got to the end of the tank. Back to Shell 93.

I just noticed that I didn't include the octane for the BJs gas in this post. It was BJs 93.

 

[MisterMac]

I just noticed that I didn't include the octane for the BJs gas in this post. It was BJs 93.

The only difference with the BJs is it has less detergents than top tier. It will not effect your fiel economy with one tank compared to other 93 Octane fuel

 

[stung cb]

I'm a new member here. I know this is a beat to death subject but, shouldn't new members input be welcomed?

The manual states 91 octane is only recommended. Recommend is defined as advised or suggested. It doesn't state required or mandatory. Don't you think KIA would actually state "mandatory or required to prevent engine damage and voided warranty."
Kia has its neck out for 10 years or 100,000 miles. If they say less than 91 octane is okay to burn, why would you doubt them.
Now......if you feel 91 or better is giving you better mileage and or performance (which KIA only states "may" do so) do what makes you feel comfortable. Here in the Denver area 91 octane is $.50 more per gallon over regular. The 3-5 more miles per gallon by burning 91 octane over regular that I hear seems like quite a push. But, I could be wrong.

 

[Aarvix]

But I can't run map5 on 87...E30 on the other hand...

 

[SafetyPilotCal]

I'm a new member here. I know this is a beat to death subject but, shouldn't new members input be welcomed?

The manual states 91 octane is only recommended. Recommend is defined as advised or suggested. It doesn't state required or mandatory. Don't you think KIA would actually state "mandatory or required to prevent engine damage and voided warranty."
Kia has its neck out for 10 years or 100,000 miles. If they say less than 91 octane is okay to burn, why would you doubt them.
Now......if you feel 91 or better is giving you better mileage and or performance (which KIA only states "may" do so) do what makes you feel comfortable. Here in the Denver area 91 octane is $.50 more per gallon over regular. The 3-5 more miles per gallon by burning 91 octane over regular that I hear seems like quite a push. But, I could be wrong.

In the 2018 manual, Kia stated matter-of-factly that the car was "designed to use only unleaded fuel having a pump octane number (R+M/2) of 87 (RON 91) or higher." In 2019 and 2020 this was changed to the "recommended" line that you point out. In the very next paragraph it says "Using unleaded gasoline with an octane rating lower than RON 95 [91 R+M/2] could result in loss of engine power and increase in fuel consumption".

So a few of things could have happened. Kia could have made a change to the ECU calibration in 2019 and 2020 that makes 91 more suitable. Maybe in further testing they determined that 91 resulted in better overall performance, economy, and drivability. Most performance vehicles use the "recommended" wording, including my Corvette. At the end of the day, the drives "fine" on regular.

That being said, it's a twin turbo, moderately-high compression V6. I'd certainly feel stupid if the $7 per fill up I saved by not using premium fuel resulted in engine damage from detonation. Even if it didn't, I paid good money for the power the Stinger offers, I'm not sure why I'd run low grade fuel (outside of long highway trips) to save a few pennies but get worse performance and fuel economy.

 

[RUFFSTUFF]

If you run 87, the ECU will change the calibration to suit. The end result is not beneficial. If paying for Premium fuel is an issue, a Kia Optima 2.0L will run all day on 87... Just a suggestion.

 

[MisterMac]

If you run 87, the ECU will change the calibration to suit. The end result is not beneficial. If paying for Premium fuel is an issue, a Kia Optima 2.0L will run all day on 87... Just a suggestion.

The end result of running 87 vs 91+ is neither detremental or beneficial. It is net neutral.