amirza786
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I was at Costco the other day filling up when one of my co-workers pulls to the empty pump in front of me in his 2013 Toyota Corolla. I notice that he selects the 91 octane button, I did't say anything. When I got to the office I ran into him and I said hey Ed (let's call him Ed), I noticed you filled up with Premium. He smiles and says yeah, I use Premium sometimes to get better performance. I asked him what does the manual say to use, and he says 87, but he sometimes likes to use 91 to periodically "clean out" his engine and it runs a lot better when he uses Premium. He looked really convinced, so I just said OK and went back to my desk.
Like Ed, a lot of people have a huge misunderstanding when it comes to octane ratings, and have preconceived notions that premium gasoline smooths out engines better, gives them more power, and cleans their engine better, although their cars call for 87. So why is it our 1.5L Turbocharged engines do much better on premium than 87? And do even better on E40 or E85 when flex fuel kits are installed and the engine is properly tuned?
The truth is, 91, 93 and even 100 octane gas does not contain more energy than 87. there is not more bang for the buck, so to speak. The difference between the three octane levels is volatility, or how much heat or compression it takes to ignite it, and 87 wins in this category. Gasoline and air are compressed before they are sent to the cylinder, and in higher performance engines or those that are turbocharged or supercharged are compressed even higher, so if gasoline is to volatile, it will ignite to soon (pre-igntion) in the cycle causing knocks and pings and worse, Low Speed Pre-ignition (LSPI).
So why is it that when we put 87 octane in our Si's there is less power? When the ECU detects 87 octane, it wants to prevent knocks and pings and worse, LSPI, so it pulls back on timing, which in turn lowers performance and response. The same energy that is present in 91 or 93 is there, only those octane levels take much hotter conditions to ignite, those same conditions would pre-ignite 87 much sooner, possibly causing engine problems without the intervention of the ECU. With 91 or 93, the engine does not have to pull back performance to prevent knocks and pings, as there is no longer the issue with pre-igniting the fuel/air mixture to early
What about those who's engines that require 87 and they use 91 or 93? In most cases you are just wasting money and are gaining zero benefit, and in some cases you may be harming your engine in the long run as higher octane gas may not fully ignite due to its higher volatility, so you will have unburned gas left over
So to summarize, the difference between 87, 91 and 93 is volatility, with 87 being highly volatile as compared to higher octane gasoline's, which makes it unsuitable for many high performance engines that run hotter, further compress air and gas mixtures, and require higher octane gas. Basically, if your car calls for 87, you are not gaining any benefit from using a higher octane gas, wasting money, and in some cases may even be causing harm to your engine in the long run
Like Ed, a lot of people have a huge misunderstanding when it comes to octane ratings, and have preconceived notions that premium gasoline smooths out engines better, gives them more power, and cleans their engine better, although their cars call for 87. So why is it our 1.5L Turbocharged engines do much better on premium than 87? And do even better on E40 or E85 when flex fuel kits are installed and the engine is properly tuned?
The truth is, 91, 93 and even 100 octane gas does not contain more energy than 87. there is not more bang for the buck, so to speak. The difference between the three octane levels is volatility, or how much heat or compression it takes to ignite it, and 87 wins in this category. Gasoline and air are compressed before they are sent to the cylinder, and in higher performance engines or those that are turbocharged or supercharged are compressed even higher, so if gasoline is to volatile, it will ignite to soon (pre-igntion) in the cycle causing knocks and pings and worse, Low Speed Pre-ignition (LSPI).
So why is it that when we put 87 octane in our Si's there is less power? When the ECU detects 87 octane, it wants to prevent knocks and pings and worse, LSPI, so it pulls back on timing, which in turn lowers performance and response. The same energy that is present in 91 or 93 is there, only those octane levels take much hotter conditions to ignite, those same conditions would pre-ignite 87 much sooner, possibly causing engine problems without the intervention of the ECU. With 91 or 93, the engine does not have to pull back performance to prevent knocks and pings, as there is no longer the issue with pre-igniting the fuel/air mixture to early
What about those who's engines that require 87 and they use 91 or 93? In most cases you are just wasting money and are gaining zero benefit, and in some cases you may be harming your engine in the long run as higher octane gas may not fully ignite due to its higher volatility, so you will have unburned gas left over
So to summarize, the difference between 87, 91 and 93 is volatility, with 87 being highly volatile as compared to higher octane gasoline's, which makes it unsuitable for many high performance engines that run hotter, further compress air and gas mixtures, and require higher octane gas. Basically, if your car calls for 87, you are not gaining any benefit from using a higher octane gas, wasting money, and in some cases may even be causing harm to your engine in the long run
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