Octane in the US questions:

[Gunter]

A long drive through Washington, Idaho, Montana, Utah, Arizona made me aware of different octane ratings at various outlets.
In some States, Chevron offered 92, and sometimes only 91.
On the other hand, Sinclair offered 93 in some places.

Some stations post the addition of Ethanol for Winter months; or even all the time.
The questions is: Does every State have it's own laws regarding octane?
No Federal jurisdiction?

I usually look for Chevron but, if other Companies offer a higher octane rating in certain States, what's the catch?

Any thoughts on why not use Sinclair, or Arco, Sunoco or any other place if they offer a higher octane?

Thanks.

[tcar]

Octane differences have to do mainly with altitude, not brand.

Sea level typically has 87, 89, 93 octane

Here in Denver (Mile above sea level) we have 85, 87, 91.

91 here is the same as 93 at sea level. If an engine requires 93 at sea level, it will require only 91 in Denver.

There is less air pressure the higher you go.

[gerrygug]

The following information was lifted from the California Energy Commission website. As you can see there are more types of gas than you can imagine. The formula will vary by state and time of year as follows:

Finished Motor Gasoline: A complex mixture of relatively volatile hydrocarbons with or without small quantities of additives, blended to form a fuel suitable for use in spark-ignition engines. Finished Motor Gasoline includes conventional gasoline; all types of oxygenated gasoline, and all types of reformulated gasoline, but excludes aviation gasoline.

Reformulated Gasoline: Finished motor gasoline that is formulated to reduce emissions of various criteria pollutants from motor vehicles.

* California Reformulated Gasoline (CA RFG): Finished motor gasoline formulated for use in motor vehicles, the composition and properties of which meet the requirements of the reformulated gasoline regulations promulgated by the California Air Resources Board (CARB). This type of finished gasoline usually contains 5.7% ethanol as an oxygenate or in a few areas may contain no oxygenate (CARB RFG Non Oxy). This category excludes California reformulated gasoline blendstock for oxygenate blending (CA RBOB).


* EPA Reformulated Gasoline (RFG): Finished motor gasoline formulated for use in motor vehicles, the composition and properties of which meet the requirements of the reformulated gasoline regulations promulgated by the EPA to meet requirements of the Clean Air Act. This category excludes reformulated gasoline blendstock for oxygenate blending (RBOB).


* Arizona Cleaner Burning Gasoline (Arizona CBG): Finished motor gasoline formulated for use in motor vehicles, the composition and properties of which meet the requirements of the cleaner burning gasoline regulations promulgated by the state of Arizona. This type of finished gasoline may contain MTBE (Arizona CBG - MTBE) or no oxygenate (Arizona CBG Non Oxy). This category excludes Arizona reformulated gasoline blendstock for oxygenate blending (AZ RBOB).


* Nevada Cleaner Burning Gasoline (LVCBG): Finished motor gasoline formulated for use in motor vehicles, the composition and properties of which meet the requirements of the cleaner burning gasoline regulations promulgated by the state of Nevada. This category excludes Nevada's cleaner burning gasoline blendstock for oxygenate blending (CBGBOB).




Oxygenated Gasoline (not classified as reformulated gasoline outside of California, Arizona or Nevada): Finished motor gasoline that contains an oxygenate. This type of finished gasoline is primarily used during the winter months in regions of the United States that are not in compliance with carbon monoxide standards. Other areas may mandate the use of oxygenates during a portion of the year to help control other types of air pollutants. Oxygenates can also be mandated for use to achieve compliance with minimum use goals.

* EPA Winter Oxygenated Gasoline: A finished gasoline that contains a minimum of 1.8% oxygen by weight. This type of finished gasoline is mandated for use during the winter months in areas of the United States (other than California, Arizona and Nevada) that are not in compliance with federal carbon monoxide standards.


* Arizona Winter Gasoline: A finished gasoline that contains ethanol at a concentration of 10% by volume. This type of finished gasoline is mandated for use during the winter months (November through March) in certain areas of Arizona. Prior to blending with ethanol, the unfinished base gasoline is referred to as Arizona Blendstock for Oxygenate Blending (AZBOB).


* Nevada Winter Gasoline: A finished gasoline that contains ethanol at a concentration of 10% by volume. This type of finished gasoline is mandated for use during the winter months (October through March) in Clark County. Prior to blending with ethanol, the unfinished base gasoline is referred to as Nevada Blendstock for Oxygenate Blending in Las Vegas (LVBOB).


Conventional Gasoline (not classified as oxygenated or reformulated gasoline): These types of finished gasoline do not contain any oxygenates.

* Arizona Conventional Gasoline: Finished motor gasoline formulated for use in motor vehicles. This type of finished gasoline is for use in areas of Arizona not required to use Arizona Cleaner Burning Gasoline.


* Nevada Conventional Gasoline: Finished motor gasoline formulated for use in motor vehicles. This type of finished gasoline is for use in areas of Nevada not required to use Nevada Cleaner Burning Gasoline.


* Other Conventional Gasoline: Finished motor gasoline formulated for use in motor vehicles. This type of finished conventional gasoline is for use in areas outside of California, Arizona and Nevada or for use as an exempt fuel in California.

[GH85Carrera]

I suspect every state does it's own thing. Here in Oklahoma 99.8% of the stations sell 91 as premium. There are a few hard to find placed that sell 93 but at a big cost. One new law goes into effect July 1st. It requires all stations to post the alcohol content on the pump. For whatever reason there are no Chevron stations in the state.

[Scooter]

I just drove my 993 from Washington to Texas via Oregon, California, Arizona and New Mexico and I can tell you that there is definitely a big difference in performance from altititude and octane levels. I purchased Cheveron Supreme in every location (I filled up in every State). I started getting pinging in New Mexico and Texas from lower octane (91 in Arizona and New Mexico). I called a well-known mechanic about the pinging and he told me that 993s should not be run on 91 octane fuel. 92 is the minimum recommended under normal conditions here in Texas and a 50/50 mix of Supreme and race gas is recommended for track days. Now, I don't know if this is true, but as soon as I filled up with 93 here in Texas, the car has been very happy.

[tcar]

Don't know your route, but if you fill w/ 91 in northern NM, Santa Fe, ABQ, etc., then drive South, you will get pinging as your altitude decreases rapidly toward Texas.

993 does not need 92 or 93 at a mile above sea level.

Also, your performance decreases at about 4% (I read somewhere) per 1000 feet increase in altitude.

[burgermeister]

Originally Posted by tcar

Octane differences have to do mainly with altitude, not brand.

Sea level typically has 87, 89, 93 octane

Here in Denver (Mile above sea level) we have 85, 87, 91.

91 here is the same as 93 at sea level. If an engine requires 93 at sea level, it will require only 91 in Denver.

There is less air pressure the higher you go.

Wouldn't a turbo require the same octane, even at higher altitude, since it just adds more boost to make up for the thinner air? Or does it limit boost by pressure relative to 'ambient' (so basically, there is less boost at high altitudes)? Or does it depend on the car?

Just in case one day, far far away, in a lala land not yet envisioned, I end up with one ...

[Scooter]

Originally Posted by tcar

Don't know your route, but if you fill w/ 91 in northern NM, Santa Fe, ABQ, etc., then drive South, you will get pinging as your altitude decreases rapidly toward Texas.

993 does not need 92 or 93 at a mile above sea level.

Also, your performance decreases at about 4% (I read somewhere) per 1000 feet increase in altitude.

I drove staight down the 10 freeway, which would be the southern parts of AZ, NM and TX. I was experiencing pinging at the lower altitudes.

[tcar]

On I-10, 91 is low, especially if it was hot.

But I know (as you do) in parts of AZ, NM, that's all you can get.

[Porsche-O-Phile]

I'd still love to know why CA (with its militant pursuit of better air quality) only uses a maximum of 91 octane versus 93 or 94 in most states east of here. I'd think the 93/94 would allow vehicles (particularly high compression) to run better/cleaner and with more complete combustion.

Newer vehicles especially will adjust timing advance/retard based on the octane of the fuel detected to (1) prevent detonation and (2) maximize performance. As such, the lower R+N/2 number for so-called "premium" gas here might actually result in a lot of newer cars running with timing slightly more retarded than they would with higher 93 or 94, with the benefits of more complete combustion, etc.

Seems to me the only thing "premium" about CA gas is the price tag. Or am I getting too worked up about nothing and it's "just a number"?

Just seems weird that CA seems to deliberately use "inferior" gas to a lot of the eastern/midwestern states.

[Aerkuld]

Originally Posted by Porsche-O-Phile

I'd still love to know why CA (with its militant pursuit of better air quality) only uses a maximum of 91 octane versus 93 or 94 in most states east of here. I'd think the 93/94 would allow vehicles (particularly high compression) to run better/cleaner and with more complete combustion.

Newer vehicles especially will adjust timing advance/retard based on the octane of the fuel detected to (1) prevent detonation and (2) maximize performance. As such, the lower R+N/2 number for so-called "premium" gas here might actually result in a lot of newer cars running with timing slightly more retarded than they would with higher 93 or 94, with the benefits of more complete combustion, etc.

Seems to me the only thing "premium" about CA gas is the price tag. Or am I getting too worked up about nothing and it's "just a number"?

Just seems weird that CA seems to deliberately use "inferior" gas to a lot of the eastern/midwestern states.

Hving had to deal with CARB regulations with my job it soon becomes clear that the people who make the legislation do not understand the science.