Why different Octane Ratings for Premium?

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Hello all,

I've tried looking into this but haven't been able to find a concrete answer so I figured I'd turn to the BITOG community. I've had a few vehicles that recommended 89 octane "mid-grade" gasoline, the Alfa is the first that has recommended 91 octane "premium". I've noticed at the two pumps I've stopped at (Mobil & Costco) that their premium is 93 octane. Per the manual, the Alfa can use 87 octane but it is recommended to run 91. I'm sticking to their recommendation and using a minimum of 91, unless no options are available.

With that being said, why is there a seemingly lenient system of deciding what octane rating constitutes as premium? I understand that with the exception of some western states, regular is mandated at 87 octane. Is this not the case for the other grades? Or is 91 the mandate and anything equaling or higher (within reason) gets the same label?
 
Originally Posted by RamFan
Or is 91 the mandate and anything equaling or higher (within reason) gets the same label?


This. Except for high altitudes, where premium might be 89 or 90.
 
The old theory was that there was more demand for super on the West coast so you get 91 there and there's less on the east coast so you end up with 93. But as long as it's at least 91, you're fine.
 
There's nothing lenient nor mandated, whatever a particular retailer or refiner decides to sell is labeled with the octane rating. Likewise they price it as desired. Premium grade is not a technical term, it is only used to denote the highest octane available at a retailer - whatever that might be.

Generally the reason one premium grade might be 93 as opposed to 91 octane is due to the presence of ethanol.
 
Originally Posted by Snagglefoot
Its marketing. They can capture many different tiers of consumers by offering various octane ratings.

My ECHO and Accord only require 87 and my BMW requires 89. The Sienna requires 87 but also states that higher octane will improve performance. How is that "marketing"?
 
Some stations sell higher octane for engines tuned up more than manufacturers sell. Lots of people with turbo cars will run a 93 or 94 octane tune if that's the highest available locally. I found I was getting a bit of ping on 91 on my old YZ250. 94 octane seems to cure it.
 
I was always under the impression that the retailers are just playing it safe and advertising the minimum octane of that level of fuel, different altitudes I thought affected performance. So it may actually be 93 in the tank, but they say 91 for testing or degradation. But this is only speculation, Im interested to know the truth as well.
 
Originally Posted by kschachn
Originally Posted by Snagglefoot
Its marketing. They can capture many different tiers of consumers by offering various octane ratings.

My ECHO and Accord only require 87 and my BMW requires 89. The Sienna requires 87 but also states that higher octane will improve performance. How is that "marketing"?


Believe it or not, most "Premium Fuel" is purchased by folks who do not drive vehicles that require Premium Fuel. The marketing departments are well versed with this. Just watch the folks at pumps. You'll see many of them selecting higher grades than their cars require.
 
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91 octane no alcohol gas becomes 93 or better with the addition of alcohol. Around here, I have not been able to find no alcohol 93
 
Originally Posted by Snagglefoot
Originally Posted by kschachn
Originally Posted by Snagglefoot
Its marketing. They can capture many different tiers of consumers by offering various octane ratings.

My ECHO and Accord only require 87 and my BMW requires 89. The Sienna requires 87 but also states that higher octane will improve performance. How is that "marketing"?


Believe it or not, most "Premium Fuel" is purchased by folks who do not drive vehicles that require Premium Fuel. The marketing departments are well versed with this. Just watch the folks at pumps. You'll see many of them selecting higher grades than their cars require.


Those aren't requirements! They are thresholds/warnings not to go below that number. Do you see them NOT recommending a higher octane?
 
No more 92: Premium octane rating drops in California

https://autoweek.com/article/car-news/no-more-92-premium-octane-rating-drops-california

While it's hardly news compared to rolling blackouts, Californians are now dealing with another energy crisis: In August, the octane rating of premium gasoline in the state quietly dropped from 92 to 91.

For many, the drop in octane won't make much of a difference, as most late-model vehicles that need premium fuel only require 91—and most will even run on 87, albeit with reduced performance when the knock sensor kicks in and retards the timing. Hardest hit: Owners of older, carbureted cars and trucks or those running hot-rodded engines; it's hard to lower compression once you've dropped in those flat-top pistons.

And the owners of Porsches with fuel filler flaps that clearly recommend 93 octane? Don't worry, your cars are designed to accommodate fuel as low as 91 (it says so in your owner's manual). And the difference between 92 and 91 isn't all that great.

"I don't think you will notice," says Walter Lewis, Porsche senior compliance engineer. "On a dyno you might, but it would be very minor."

Okay, but what happened? Another Big Oil conspiracy? The work of the notorious California Air Resources Board? Well, as is anything involving energy and California, it's complicated.

It started when Kinder Morgan, the company that owns the primary gasoline pipeline in California, surveyed its customers in April. Spokesperson Rick Rainey says Kinder Morgan asked over 100 refiners and distributors how the company could better serve them; nearly all of them asked to start running 91-octane premium through the pipeline instead of 92. On Aug. 1, Kinder Morgan made the switch. As the vast majority of gasoline sold in the state at some time travels through this pipeline, 92 in California disappeared as quickly as a Barry Bonds line drive.

So it's that simple—until you ask "Why?"

First, there's the environmental angle. California Gov. Gray Davis banned the use of gas additive methyl tertiary butyl ether in the state by 2003. MTBE is a carcinogen that can leak into and contaminate ground-water, but it's also the primary oxygenate additive that California refiners use in reformulated gasoline. It also boosts octane; thus it's useful in blending premium gas.

The impending ban has created a widespread fear of gasoline shortages. According to Chevron repre-sentative Lou Gibbs, this is because the planned MTBE replacement, ethanol, cannot be added to gasoline in as high proportion as MTBE; thus the total capacity of the refineries will be reduced. The refineries are already running at full capacity today, says Gibbs, so the move to 91 is a step to stave off the perceived shortfall.

Of course, there's another side to the story, one that's more about money. In 1994, Unocal was awarded the first of five patents for reformulated gasoline, none of which use an oxygenate additive like MTBE or ethanol. Most major refiners are loath to license the formulas, as evidenced by a six-year legal battle over the validity of the initial patent, one that Unocal won. But, as Gibbs explains, Unocal's patents for premium gasoline are for the 92-octane variety; 91 is not covered. Therefore, the switch to 91 may just be an end-around by the refineries to avoid paying licensing fees.

The story may not be over, though it seems likely Californians will have to live with 91 as the peak octane. Recent reports, however, indicate that the infrastructure necessary to handle ethanol in the required volumes doesn't yet exist—and there's some question about whether ethanol can be produced in sufficient quantity to supply California's demand—so Gov. Davis may push back his 2003 ban on MTBE.
 
Originally Posted by Snagglefoot
"Midgrade" is for non Bitgoers who absolutely know nothing about gasoline. They are just pressing the button between the other two.

Kind of like people who don't know how to take pictures. Just pressing the button.
 
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