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If you know what "octane" means within the context of auto fuel the question is moot

https://www.exxon.com/en/octane-rating

Octane rating is a measure of a fuel's ability to resist ‘knock’. The octane requirement of an engine varies with compression ratio, geometrical and mechanical considerations and operating conditions. The higher the octane number the greater the fuel’s resistance to knocking or pinging during combustion.

The recommended octane rating for most vehicles is usually octane 87, but be sure to check your vehicle owner’s manual. Ordinarily, a vehicle will not benefit from using an octane higher than recommended in the owner’s manual.


octane rating does not change the temperature at which the fuel burns. (saw this one in a previous post)


if you car has a "tune", this may have over written the standard programming of the fuel/ignition system such that normal ping sensors are no longer working and higher octane may be required. In the stock setup, the computers can deal with the potential for knock.

When I fill for routine driving I use "regular"

when planning a road trip or a situation where I may be 'stomping it' and the engine MIGHT reach peak compression, then I fill with PLUS ... only then
 

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I'm tuned for 93 and at times I get corrections on my tune and my Octane Adjust Ratio changes for the crappy fuel. So bad sometimes that I can put Octane Booster in it to get it back to 93. Sad life we live with our winter blend and performance cars. Stock cars won't notice it as bad, but it's definitely gross fuel compared to summer. I averaged 240 miles my last tank grannying it.
So this is the same even here in the deep south where it's still 75 most days this time of year?
 

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So this is the same even here in the deep south where it's still 75 most days this time of year?
I was told by someone on here who's extremely knowledgeable about this fuel stuff that the country has different predetermined areas which get different blends. So down south it's not nearly as bad, but we all get a different blend for sure so it's technically worse for you guys in the winter than summer but not nearly as bad.
 

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Fuel blends are climate driven hence why the South is least affected by winter blend changes. On average you loose about 2% of your energy density with winter blended fuels, octane ratings do not change from what is displayed. The reasons for the compositional changes is more then just Reid Vapor Pressure, it has a lot to do with politics, hydrocarbon distillate fractionation inventory, and local/state regulations resulting on close to 25 different formulations for public use. I have a little bit more insight on this then most since I am a formulations and materials chemist in the petroleum industry. Most of the bad gas is caused by stations that are neglegent in how they handle the fuel and maintain their delivery and storage systems. Stay away from stations that are slow business and avoid getting gas while being tanker filled.

If you are constantly coming across "bad gas" then report it for testing. While refining QA/QC issues are very rare, they do happen. Most of the time it's related to fractionation cross contamination or similar.
 

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One thing I forgot to point out is that certain areas of the country are required by the EPA to use a special blend of gasoline year round. Reformulated Gasoline (RFG) is used in these pollution prone areas because it contains more oxygenates than ordinary gasoline. The refinery where I worked made a couple of different blends of RFG specifically for these regions.
 
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