A Reason to Buy Premium Fuel

Where are you seeing that much of a spread?

It's always been interesting where over the years I've typically seen a 10 cent difference between 87/89/91(or 92 when it was a thing around here). I was in Arizona years a couple of decades ago and it was .799/.899/.999 per gallon. That was the most common price spread (10 cents) for decades, although a lot of places vary these days, although it's still typically less than a 10% difference.
You're right. I checked a few stations in the Bay Area and the price spread is under 10%. Where I fill up (Costco), it fell down to a 17% spread. A quick check on other stations in my area shows a similar spread. It appears the differences are regional.

The spread is significant enough for me the continue using regular. My goal is to keep my cost of going from point A to point B at a minimum.
 
They recommend premium. They all have knock sensors, so I'm not worried about ruining the engine.
Knock sensors report to the ECU which most all OEM ECU programs are very limited to adjusting all that is needed to protect the engine and for the knocking condition medium and severe engine knock all your doing is pounding the engine .

You can get cheap low quality OBD-II access monitoring and find knock sensor values. Then go see what happens between 87 and 91-93 or higher values. Return as say the use of higher then 87 octane fuel is not perhaps a wiser choice overal and especially with engines in the 75-100k miles category.
 
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You're right. I checked a few stations in the Bay Area and the price spread is under 10%. Where I fill up (Costco), it fell down to a 17% spread. A quick check on other stations in my area shows a similar spread. It appears the differences are regional.

The spread is significant enough for me the continue using regular. My goal is to keep my cost of going from point A to point B at a minimum.

I don't necessarily understand how it all works out. I did find it interesting when the 10 cent price spread was the standard. It only showed that pricing wasn't necessarily related to cost. I remember even hearing at one point that premium typically cost marginally more (maybe a few cents per gallon) wholesale than regular, but the pricing model was designed to make more profit from selling premium even if it cost more.

But with the price of gas more than $3/gallon I'm seeing a lot different price spreads now.
 
Not true anymore with the advent of top tier, which requires the same detergents in all grades of gasoline :unsure:

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Not true. it requires the same minimum level of performance requirements over the federal requirements. Top Tier doesn't stop gasoline providers from making their 91/93 AKI premium over 87/89, as a long as all of the levels meet the Top Tier performance requiremnent
They recommend premium. They all have knock sensors, so I'm not worried about ruining the engine.

Yes, knock sensors will pull back on timing, etc... but the ECU will always try to revert back to its specified tuning until it gets knock again, then the vicious circle repeats over and over again, until you put enough of the AKI back in and it doesn't need to pull back on timing, etc.
 
Knock sensors report to the ECU which most all OEM ECU programs are very limited to adjusting all that is needed to protect the engine and for the knocking condition medium and severe engine knock all your doing is pounding the engine .

You can get cheap low quality OBD-II access monitoring and find knock sensor values. Then go see what happens between 87 and 91-93 or higher values. Return as say the use of higher then 87 octane fuel is not perhaps a wiser choice overal and especially with engines in the 75-100k miles category.
Yup, knocking is not good for the engine and can lead to damage if left unchecked, even light knocking. Knock sensors only prevent catastrophic damage (like a broken ringland etc) from severe uncontrolled knock.
 
Not true. it requires the same minimum level of performance requirements over the federal requirements. Top Tier doesn't stop gasoline providers from making their 91/93 AKI premium over 87/89, as a long as all of the levels meet the Top Tier performance requiremnent


Yes, knock sensors will pull back on timing, etc... but the ECU will always try to revert back to its specified tuning until it gets knock again, then the vicious circle repeats over and over again, until you put enough of the AKI back in and it doesn't need to pull back on timing, etc.
Yes this is somewhat accurate. Unfortunately when you cause a constant input information to the ECU it’s called adaptive. Once you do this it can take several complete engine cycles to change them back to best or base line programming operation. Unless you clear the adaptive sin the ECU. The proper way is to either flash the ECU or access and reset the ECU via the OBD-II connector.
Knock sensors are always misunderstood and many think they will save the engine if knock is present, constant and extreme. They don’t !
 
They recommend premium. They all have knock sensors, so I'm not worried about ruining the engine.
Recommended and required are very different… my truck recommends 89 but I can’t tell a difference when running 87. A 6.4 SRT or Hellcat requiring 91 minimum is going to have a very bad time on 87.
 
if your vehicle doesn’t require higher octane fuel then you don’t get any gains from it. If you’re having to run a higher octane fuel in a vehicle that doesn’t require it then your vehicle must be running hot or the combustion chamber has a lot of carbon buildup.
 
My 18 F150 5.0 recommends 91. It will run on 87 and I’ve done it before I read the manual but it runs like a different truck on 93. No 91 here.
 
The issue is that there are presumptions made when the word "premium" fuel is discussed. "Premium" fuel is not a regulated word, nor a regulated product in the retail fuel industry. Premium fuel may have some elements that are regulated, but they are not limited to having only those minimums or maximums, etc. They can be "better", but better does not always result in tangible results.

Octane is an element that helps resist compresion related per-detonation. Octane does not increase or improve the energy density in the fuel. It is helpful in higher compression-ratio gas engines which can benefit from advancing the spark timing, as long as the octane level can sustain the proper flame propogation and not pre-ignite. Higher octane fuels do not improve combustion past the level needed for the engine requirement. "Required" is not the same a "recommended". As discussed in posts above, the anti-knock sensors will retard spark timing to prevent engine damage. It is beneficial to pick a fuel grade and run that same level all the time, versus trying to jump up/down the choices, because the ECUs are trying to keep a constant level of performance and benefit from steady inputs. In short, if your car does not require or recommend high octane, it won't benefit from it. Much older engines may actually have experienced a CR increase due to carbon build-up on the piston and head surfaces, and while they may have been rated for 87 when new, they may benefit from 89 two or three decades later. But a really good dose (or doses) of high-quality detergent fuel additives can help remove some of that build up (some of the top Gumout products and Techron have huge amounts of PEA and can clean the chamber well). But that's octane related ... there are other fuel characteristics to discuss as well.

Top Tier fuels are required to meet minimum standards, not by governmental decree but by market-based automotive engineering intent. These fuels deal mainly with standards to hold a desired level of cleanliness in the engine as supported by the fuel in terms of the combustion process, and to a degree, also the cleaning effect of the raw fuel washing valvetrain components (intake tract). To the best of my knowledge, TT fuels do not address fuel power density; they are a content standard relative to making the engine run cleaner. Any fuel brand licensed for TT will have that minimum level of cleaning elements to maintain the licensed levels required. They can have "more", but they cannot have less than the standard. That standard is good enough for most applications, but some applications can benefit from "more".

Because "Premium" fuels are not limited to the minimums, they can have "more" of certain things. They can have more detergents, they can have more octane, etc. Premium fuels can have more energy density by manipulating the blend. But that energy density is not directly related to the detergents, anti-oxidants, or octane; it's a separate topic speficially defined by the chemicals related to fuel combustion energy. So, though one's car may not "need" or even benefit from the higher octane in a premium fuel, the other elements added to premium fuel (typically more cleaners and more anti-oxidants) can still add a benefit, despite not always needed the higher octane. But even these are only helpful in some situations and not all. The other benefits found in premium fuels past octane may or may not be of real benefit. Some engines run fairly clean; they may not need the "extra" cleaners above the TT minimums. Further, cars that are driven regularly won't benefit from the extra anti-oxidants; they will cycle the fuel loads often enough that degradation really isn't a big risk. There are times when premium fuels can be of great benefit. For example, using a premium fuel will have more beneficial effect for long-term storage fuels used in seasonal items such as lawn and garden equipment, snow blowers, chainsaws, etc.

Here's my summary of the fuel topic:
- fuel energy density
- cleaning agents
- anti-oxidants
- pre-detonation elements
- environmentally friendly enhancements
All these things play into the fuel factors. Premium fuels will have more of certain desirable characteristics, but your car may or may not benefit from those elements, depending upon a large list of "what if ..." conditions.
 
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You could possibly need it if your vehicle isn't getting refueled enough. I think after three weeks and maybe sooner in high humidity conditions that ethanol blended fuel would start to break down and loss their octane. My mother is semi disabled so if I borrow the new CRV with the 1.5T then after I am done I top it off with premium non ethanol to help out. I thought some of the big name companies like Chevron use a more stout additive for their higher octane fuels. In sure that there is some faux marketing in the Shell promotion, but at one time or another many people fell for the same BS with Seafoam or Lucas Oil Stabilizer.
 
You could possibly need it if your vehicle isn't getting refueled enough. I think after three weeks and maybe sooner in high humidity conditions that ethanol blended fuel would start to break down and loss their octane. My mother is semi disabled so if I borrow the new CRV with the 1.5T then after I am done I top it off with premium non ethanol to help out. I thought some of the big name companies like Chevron use a more stout additive for their higher octane fuels. In sure that there is some faux marketing in the Shell promotion, but at one time or another many people fell for the same BS with Seafoam or Lucas Oil Stabilizer.

Someone posted a hand treat rate table for Chevron if there's a problem with the delivery of the additive at the fuel terminal. It could be higher, but since entire bottles were dumped in to simplify it, it wasn't precise. But when treated right on the dot of maximum ratio of fuel to additive, I think it was something like 500 gallons of fuel per bottle of Techron bulk additive for regular/mid and 400 gallons fuel for "Supreme".
 
Octane is an element that helps resist compresion related per-detonation. Octane does not increase or improve the energy density in the fuel. It is helpful in higher compression-ratio gas engines which can benefit from advancing the spark timing, as long as the octane level can sustain the proper flame propogation and not pre-ignite. Higher octane fuels do not improve combustion past the level needed for the engine requirement. "Required" is not the same a "recommended". As discussed in posts above, the anti-knock sensors will retard spark timing to prevent engine damage. It is beneficial to pick a fuel grade and run that same level all the time, versus trying to jump up/down the choices, because the ECUs are trying to keep a constant level of performance and benefit from steady inputs. In short, if your car does not require or recommend high octane, it won't benefit from it. Much older engines may actually have experienced a CR increase due to carbon build-up on the piston and head surfaces, and while they may have been rated for 87 when new, they may benefit from 89 two or three decades later. But a really good dose (or doses) of high-quality detergent fuel additives can help remove some of that build up (some of the top Gumout products and Techron have huge amounts of PEA and can clean the chamber well). But that's octane related ... there are other fuel characteristics to discuss as well.

Just one little quibble. I don't think that gasoline necessarily has to contain octane. What we describe as "octane rating" is just about anti-knock performance relative to a reference fuel made with varying amounts of iso-octane and n-heptane. Not sure why these two have become the standard for the reference, although I've heard n-heptane described as causing extreme knock if the sole fuel. I guess 100% n-heptane would have an octane rating of 0. I'm not quite sure how it works for fuels that have an octane rating higher than 100.

 
I'm not quite sure how it works for fuels that have an octane rating higher than 100.
It has been a while since I ran that test but the range has always been higher than 100, that's just the number that is assigned to isooctane. IIRC it goes up to 120 or something for other fuels or mixtures (isooctane and TEL for example).
 
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It has been a while since I ran that test but the range has always been higher than 100, that's just the number that is assigned to isooctane. IIRC it goes up to 120 or something for other fuels or mixtures (isooctane and TEL for example).

I understand that. But my understanding is that the way of doing it by comparing it to a blend of iso-octane and n-heptane obviously doesn't work any more once it's pure iso-octane.
 
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