Far too often do we need to explain to people why to ONLY use factory recommended octanes (usually its me lately). Instead of regularly typing up the same explanation and answering the same line of questioning, I'd like to make this the go-to reference thread for anytime someone asks and also a simple search reference.
This is to serve as a general reference so as to be easily understandable, so I'd like to avoid all the refined chemistry references and technical jargon. There's plenty of it online so lets just stick to the layman version for this thread. As I accrue information I will update this first thread accordingly, so don't hesitate to contribute helpful and accurate information or correct me when needed. A while back I heavily researched this for the sake of standard car usage as there was so much conflicting information, however, octane usage in performance settings are another animal I havent researched so I need the experts help on that topic.
Rule #1: The higher the octane the higher the ignition temperature & compression needed tofully properly burn the fuel. Stock ECUs cannot adjust to these differences because different components are needed to efficiently create & handle the stronger needed combustion.
Using a Higher or Lower Octane: Using higher octane than recommended leads to unburned fuel that turns into deposits throughout the injection system and beyond. That can clog and impede components over time and reduce fuel efficiency because your computer isn't programmed to adjust to that. Using lower octane than recommended can lead to pre-detonation, meaning fuel burns up too easily and doesn't create the necessary pressure to fully move the pistons, thus reduced power and efficiency. You wont get any deposit build-up but the engine will run poorly.
This is to serve as a general reference so as to be easily understandable, so I'd like to avoid all the refined chemistry references and technical jargon. There's plenty of it online so lets just stick to the layman version for this thread. As I accrue information I will update this first thread accordingly, so don't hesitate to contribute helpful and accurate information or correct me when needed. A while back I heavily researched this for the sake of standard car usage as there was so much conflicting information, however, octane usage in performance settings are another animal I havent researched so I need the experts help on that topic.
Octane in Factory / Unmodified Engines:
Rule #1: The higher the octane the higher the ignition temperature & compression needed to
Using a Higher or Lower Octane: Using higher octane than recommended leads to unburned fuel that turns into deposits throughout the injection system and beyond. That can clog and impede components over time and reduce fuel efficiency because your computer isn't programmed to adjust to that. Using lower octane than recommended can lead to pre-detonation, meaning fuel burns up too easily and doesn't create the necessary pressure to fully move the pistons, thus reduced power and efficiency. You wont get any deposit build-up but the engine will run poorly.
Octane in Modified / Upgraded Engines:
(This is not within my realm of expertise so dont hesitate to correct me or add info)
Engine upgrades such as port & polished cylinders, distributor upgrades, ignition coils, piston upgrades, higher flow injectors, turbo kits, etc. may benefit from using a higher octane because compression has been increased so stronger combustion is needed. When compression goes up you can either use a higher octane & retard timing or stay with the same octane & advance timing. Reprogramming the ECU accordingly is usually required as well. This all depends on the severity of the internal upgrades and bolt-on's. If you're tackling such mods, this line of thinking MUST be considered for it all to be done properly. (This is not within my realm of expertise so dont hesitate to correct me or add info)
Conclusion:
Stick to Factory Recommended Octane!
Or
Prepare for Problems!
Stick to Factory Recommended Octane!
Or
Prepare for Problems!
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