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this is probably a stupid question but I am paranoid about damaging my car, my 2015 forte koup sx has 2600 miles on it for the first 1500 miles I was putting 87 octane in it and after those first 1500 miles I started putting in 93 octane , today I went to the gas station and I accidently put 87 octane in it, did I do any harm to my car from switching back to 87 octane ? and is it safe to go back to 93 octane again after my car finishes the 87 octane it has in it ?
 

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No you won't harm the car. It is designed to run on 87 but the higher octane is always better for our car
 

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Since he isn't tuned or anything he will be fine with 87. Thats what Kia designed it to run on is 87. Once tuned or starting to mod the motor then 93 all the time period. The ecu is just going to pull back some timing and it won't pull as hard which sucks! lol
 

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Having LSPI blow your engine is about the same chances of winning the lottery but it only takes one glowing flake of carbon in the cylinder or one poorly timed spark while in boost and you just won. Using 93 octane will be more prone to accept the pre ignition or badly timed spark and not detonate the internals of the engine. Running 87 for normal use as a DD could be fine if there are other precautions taken like a catch can to limit the amount of oil being burned to the tops of the intake valves or in the cylinder. Yes one of the reasons this ECU has such a poor tune and runs so rich is so they could use 87. Once the ECU is properly tuned and leaned out you would never want to use 87 again only 93 or better.
You can try and win the lottery if you want but I wouldn't recommend using anything but 93.
Even when I purchased my car the dealer filled my first tank and used 93 and has been 93 since.
 
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That whole video is for regular NA automobiles and they even say that the ECU will pull timing to prevent knock or detonation when using the lower grade fuels (less timing = less power). This has nothing to do with our car but a good watch and I would say it is true for the normal NA DD but a 1.6L pushing 200+ HP is far from a normal everyday civic or cruze. The GDI does help to allow us (in stock form) to use lower grade fuels along with the shitty detuned ECU we have stock that floods the cylinders to help prevent detonation. If this was a engine with port fuel injection 18 lbs of boost on 87 octane it would be a 4 wheeled grenade under the hood. Take an old civic with a 1.6 (v-tech or not) and bolt on a 100 hp dry NOS kit with a tank full of 87 octane and you would have the same results....BOOM
 

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The only thing this proves is that the ecu in that naturally aspirated lower compression car retards the timing to compensate for the higher octane fuel.
 

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The only thing this proves is that the ecu in that naturally aspirated lower compression car retards the timing to compensate for the higher octane fuel.
Right idea but it is the opposite, The car will try to advance for the higher octane but the ECU in the NA engines won't have as much available timing as something with FI. That is why they don't see the benefits from running higher octane and is also the reason they will have more unburned fuel in the exhaust. Lower the octane the easier it is to ignite and the faster it will burn, higher the octane will take more to ignite and will have a slower burn allowing the spark plug to fire sooner (before the reaches full compression). Most NA vehicle ECUs can't advance the timing far enough to take advantage of the characteristics of the 93 so you get a late spark and a slower burn of fuel with some fuel that never gets used or burned before getting pushed through the exhaust valve and out the exhaust. Get a tune on a NA car that allows the timing to be advanced for use of 93 and it will make more power and will have less unburned fuel than stock using 87. Most NA engines (9.5.1 compression) at WOT will only see 6-8° of advance during normal operating temps, our little 9.5.1 comp engine with 18 lbs of boost can see 8-11° or better but will depend on the fuel you run.

and the guy in the Vette is a dumbass for running 87 in that car but even said it would be higher octane if it was going to the track...hmmm wonder why, maybe it's because it will perform better and make more power....?

Just remember higher octane allows for more advanced timing and more timing equals more power
 

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Right idea but it is the opposite, The car will try to advance for the higher octane but the ECU in the NA engines won't have as much available timing as something with FI. That is why they don't see the benefits from running higher octane and is also the reason they will have more unburned fuel in the exhaust. Lower the octane the easier it is to ignite and the faster it will burn, higher the octane will take more to ignite and will have a slower burn allowing the spark plug to fire sooner (before the reaches full compression). Most NA vehicle ECUs can't advance the timing far enough to take advantage of the characteristics of the 93 so you get a late spark and a slower burn of fuel with some fuel that never gets used or burned before getting pushed through the exhaust valve and out the exhaust. Get a tune on a NA car that allows the timing to be advanced for use of 93 and it will make more power and will have less unburned fuel than stock using 87. Most NA engines (9.5.1 compression) at WOT will only see 6-8° of advance during normal operating temps, our little 9.5.1 comp engine with 18 lbs of boost can see 8-11° or better but will depend on the fuel you run.

and the guy in the Vette is a dumbass for running 87 in that car but even said it would be higher octane if it was going to the track...hmmm wonder why, maybe it's because it will perform better and make more power....?

Just remember higher octane allows for more advanced timing and more timing equals more power
Right. Thanks for the correction. I was trying to get at the ecu being the reason those cars couldn't use the benefits of higher octane.

I did some more reading and found that higher octane gas simply has additives that prevent pre-ignition. One thing that can cause pre-ignition is having timing advanced too far and thus the spark ignites the fuel too early causing engine knock. Another thing that can cause pre-ignition is high compression ratio. Lower octane fuels can not handle higher compression ratios without combusting regardless of if there is a spark. This means that on cars with forced induction like ours; the higher compression means you will be more likely to get pre-ignition and the engine knock like before.

I understand a little more about octane now and thanks @Playwithmymind for your infinite wisdom as well.
 
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