California 91 octane, more detonation prone?

[Truckedup]

You California guys, do you think the 91 octane is more prone to detonation that 91 octane used in other states? I know the formulas are different...Has any one who vehicle ran fine on 91 octane in another state and went to California and used their 91 noticed any difference? Thanks

[pdq67]

No telling what brand of, "paint-thinner", Cali is using for their gasoline base-stock.

And I will say this..

Several years ago, EXXON created a great big fuels composition matrix and then patented all of the fuels in it so their competition couldn't use them. This was for Cali fuels if not mistaken? Something like 100 or so fuel composition patents...

Oh, if things continue down the road in Cali, it won't matter because they are in the process of outlawing the vehicle ICE by 2040 or so! BUT please check me here??? I read where this crap is in the works but don't know if it will actually ever be done??

pdq67

[F-BIRD'88]

I believe in California the 91 octane regulation refers to what can be advertised at the pump.. "91 octane minimum rated" ... The gas you get can actually be of higher real tested octane 92-94 but can only be sold at the pump as "91 octane".. It can be more but cannot be less than 91 octane r+m/2 gas.

But be advised. Can be more is not the same as is more than.

Yup how much paint thinner that is in that blend plays a part..

[Schurkey]

The whole R + M / 2 system is at issue. A gasoline blend that does particularly well at either R or M but does poorly with the other would still have the same averaged "pump octane" rating, but could perform very differently from a more-ordinary blend.

"Califonia" or California-similar emissions locations may have their own gasoline characteristics, but I bet it varies with the refinery, the time of year, the mood of the supervisor, the grade of available crude, and fifteen other factors I have no real idea of.

[Roundybout]

The M part of the R + M/2 is the important part of the equation for performance engines. Cold weather states at altitude have the widest variance in fuel blends depending on the season. I wish I could find the article but it was interesting how many blends there are based on geography as well as States specific mandates on fuels allowed, especially CA.

[David Redszus]

The whole R + M / 2 system is at issue. A gasoline blend that does particularly well at either R or M but does poorly with the other would still have the same averaged "pump octane" rating, but could perform very differently from a more-ordinary blend.

"Califonia" or California-similar emissions locations may have their own gasoline characteristics, but I bet it varies with the refinery, the time of year, the mood of the supervisor, the grade of available crude, and fifteen other factors I have no real idea of.

Good points all.

California has five different fuel zones depending on locations, each with different properties.
A typical 91 octane pump gas will show a RON of 96 and a MON of 86. Performance engines are much
more responsive to the MON number than to RON. The "index" is worthless.

[needforspeed66gt]

The 91 we get here is called "ACN" for Arizona, California, and Nevada - the additive package is different with more detergents in it, and is more prone to detonation than what is sold in the other states.

[stokerboats]

I've noticed this past year or more that my mileage has decreased by about 3mpg average on the present California blend which I seriously suspect has an increased amount of ethanol thus killing the mileage. Just another way for California to fleece the driver. More gas= more tax.

[NewbVetteGuy]

The whole R + M / 2 system is at issue. A gasoline blend that does particularly well at either R or M but does poorly with the other would still have the same averaged "pump octane" rating, but could perform very differently from a more-ordinary blend.

"Califonia" or California-similar emissions locations may have their own gasoline characteristics, but I bet it varies with the refinery, the time of year, the mood of the supervisor, the grade of available crude, and fifteen other factors I have no real idea of.

Good points all.

California has five different fuel zones depending on locations, each with different properties.
A typical 91 octane pump gas will show a RON of 96 and a MON of 86. Performance engines are much
more responsive to the MON number than to RON. The "index" is worthless.

David, is there a fuel zone map somewhere that meer mortals can access?
Is this variation within a state thing just an issue in California or is this a common practice in many states?


Adam

[midnightbluS10]

The M part of the R + M/2 is the important part of the equation for performance engines. Cold weather states at altitude have the widest variance in fuel blends depending on the season. I wish I could find the article but it was interesting how many blends there are based on geography as well as States specific mandates on fuels allowed, especially CA.

Yea but laboratory test conditions are in no way indicative of what happens inside of an actual high performance racing engine. It's been said that those test engines are more like a single cylinder out of a Model T than anything in a race engine. With that being said, can you really, accurately correlate the data received in the lab to what happens in a WOT, 8600RPM race engine? Reading up on octane, MON, & RON...some engines seem to show a better correlation between RON and horsepower. What would make those so different that the usual "measuring stick(MON rating)" is invalid?


Also, while reading earlier, I came across the same info that to be rated as Premium fuel, it must be at least 91 octane. It could be 91, 91.7, 93.2 or anything in between. As long as it's over 91, thats what counts. Thankfully we have 93 Octane premium gas here. Reading about Sunoco's fuels earlier, they post all of the ratings and specifications for their fuel. MON, RON, and AKI so you can get the full picture. As well as a bunch of other stuff. As an example, they said their 118 octane fuel, SR18, uses 120 and 116 blended. Keeps you from having to worry that your fuel is being blended with sub-par fuel with bottomed out MON/RON numbers. They also post specific gravity #'s. Like their Supreme 110 octane leaded fuel has a sg # that's lower than your average 87 octane unleaded pump gas, which is usually between .720 and .770 according to Sunoco. Imagine that. 110 octane fuel that probably burns as fast or faster than 87 pump gas.

[tjs44]

Even the best brand 91 in this state sucks IMO.Being a Pontiac guy and use factory iron heads,over the last 20 years or so I find that if my engines pump more than 175-180 we have detonation issues.Tom

[JCR]

David, is there a fuel zone map somewhere that meer mortals can access?
Is this variation within a state thing just an issue in California or is this a common practice in many states?

https://www.api.org/~/media/Files/Polic ... ts-Map.pdf

[In-Tech]

All I got is a blank white screen .pdf What am I missing?

[pdq67]

I haven't kept up with this, but back years ago, the St. Louis Smog Nonattainment/Maintenance Area caused them to have to use the RFG fuels.

Anyway, it was found that the evaporating ethanol coming off the pumps nozzles at fill-up time was causing problems with smog formation!! BUT nobody talked about it!! Even with the condums on the nozzles!

I laughed!!

He, He!!

pdq67

[Truckedup]

All I got is a blank white screen .pdf What am I missing?

The fuel map is US fuel requirements 2018...It appears that California has mostly one fuel zone except for a second one around what looks like LA and San Diego...
Interesting thread, lot of contrasting information..