New Member. 87 Octane gas

[Frank DuVal]

Some of the octane variation is due to how much ethanol is in the gasoline.

I call BS on that. Our pumps say "up to 10% Ethanol added" for the fuel I am talking about. The 15% and 85% are different animals not in this discussion. Your 91 is "up to 10% ethanol" too, right?

And... how is 91 at sea level in your location performing as well as 93 at sea level here?

[66vairguy]

Some of the octane variation is due to how much ethanol is in the gasoline.

I call BS on that. Our pumps say "up to 10% Ethanol added" for the fuel I am talking about. The 15% and 85% are different animals not in this discussion. Your 91 is "up to 10% ethanol" too, right?

And... how is 91 at sea level in your location performing as well as 93 at sea level here?

You answered your own question when you said ""up to 10% Ethanol added" which means anything between 0% and 10%.
I said "SOME" of the variation is due to ethanol added, NOT ALL.

If you have information on why octane varies by state, please state it.

I also said 91 octane works fine in my 140HP and in other Corvairs in our club. Why? WHO CARES it just does.

Not sure why you think only 93 octane will work --- MAYBE IT IS A CONSPIRACY -

[Frank DuVal]

I do not know why. I am trying to learn why. And no, the Ethanol statement does NOT answer my question at all, since I'm only speaking of "up to 10% Ethanol added" varieties, aka E10. Most octane variety is derived from blending different stocks at the refinery, then Ethanol is added for the final number. Since the lower octane stock is cheaper than Ethanol, that is what is added to 93/95 or so octane top end stocks to get to 91, not the Ethanol stock. For delivery from refinery to station most areas use a low octane regular fuel and a higher octane premium fuel and let the pump blend to the selected octane number. This eliminated a tank at the station. Fewer tanks, fewer rusted through leaking tanks. OK, newer tanks are fiberglass, but the piping isn't. The piping is checked at every pump cycle, why it takes so long to get the numbers in the digital display to zero.

I've only been to high altitude western places, so it seemed right to have lower octane at the pump. I have not seen Denver heads for Corvairs... I did not know sea level portions of western states were also octane limited.

Here in sea level (my house is at 250 feet above sea level) 93 octane land (most of the US east of the Mississippi*) I set timing so a 110 PG will not ping at the upshift point when it is running 93. Now what happens when the owner drives to 91 only land? I have no way to set it up to 91, or even know if the factory settings will work at 91, since with the exception of some weird 5+ choice blender pumps I've seen in Richmond I cannot fill a car with 91 to test it. That's why I need western input.

Then there are the newer GM cars that have knock sensors. I know when some 87 is added to the 93 in the tank performance drops dramatically. When the supercharger comes on the engine falls flat on its face. So out in 91 land at sea level do people just not know how the car could perform?

I'm not blaming YOU! Unless you made them stop making 93 for delivery out there...

* https://en.wikipedia.org/wiki/List_of_U ... ne_ratings