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Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted (edited)
On 8/29/2025 at 11:20 AM, newdude said:

 

 

Genuine question.  Strip away the additives to get to 87 octane, what would be raw base octane rating of "gasoline"?  So like at extraction of the base material.

 

The best "answer" I could find was from of all places, Reddit:  

 

 

"When oil is refined into various petroleum products, they use something called fractional distillation. There's a long column and oil is vaporized at the bottom of the column as heat. As the vapors travel up the tower they cool and the different weighted molecules start to condense as they get higher and higher and cool below their boiling points.

Gasoline is usually siphoned from right up near the top at about 250F, and is normally comprised of a mix of octane and heptane. What's pulled from the column is normally about 70% octane and 30% heptane, making it 70 octane rating by default. This is only rule of thumb, there are lots of other random organic compounds and hydrocarbons that are still left in fuel but they're negligible for our purposes."

 

 

Does this sound about right?  Obviously E10 and E15 fuels have the benefit of ethanol's octane rating to get to the RON at the tank (87, 89, 91, 93) so E10 and E15 probably cut down on additive use a bit?  Best I can find here for example with E10 87 octane is before they add the ethanol to the gasoline, the gasoline used is of 84 octane, then blended with 10% ethanol to achieve 87 RON.  

 

Higher Octane | Better Fuel

 

"Ethanol is Clean Octane

 

Good Ol’ Regular: Today, E10 gasolines are used in all gasoline engines. They represent nearly all gasoline sold in the United States and have been used for decades. Regular 87 octane gasoline contains 10% ethanol blended into a “sub-octane” petroleum base that has a rating of 84 octane. Ethanol boosts the resulting octane by at least three points, achieving the 87 regular gasoline. Midgrade and premium fuels, such as 91 or 93 octane, are simply 10% ethanol mixed with gasoline and higher-octane (and more expensive) petroleum compounds."

 

More internet Mumbo-Jumbo. Crude Unit straight run gasoline is an unprocessed fuel that is low octane and full of Sulphur, but the story doesn't end there. And yes can be in the 70's. Lord. And that two component blend of column cut is pure nonsense. That's the reference liquids used to determine value in the knock lab. Reagent grade materials. :idiot:

 

No one has used, sold or run straight run gasoline for many many decades and even then it wasn't 'two component'. Like your grandfathers time. Infancy of refining. It's a range, a pretty wide range. 

 

Straight run is now just a 'component' of a blend of various feed streams. The fractional distillations of units like an FCC or Isomax or Coker unit are mid to upper 80's stocks. Then units like a Rheniformer or Platformer or other catalytic type units take a blended naphtha cut stock and REFORM the molecules to reach into the 100 octane area which become part or the blend. Then units like a Isomerization Unit convert butane to iso butane as another component for RVP. Individual streams are caustic washed to remove Sulphur. And so on and so forth. I've run several of these units. There are dozens of carbon chain lengths in gasoline and why it hasn't a boiling point but rather a boiling range that the regulators use (ASTM D-86) to define it. I have run thousands of those test. 

 

Those feed streams are blended together to meet octane and governmental regulatory limits. It is a chemically define fluid just like bleach, or water. 

 

87 E-10 is and 85 stock with 9% ethanol that gives it a 2 point bump. 85 E-10 is two points lower. E-15 starts a point lower. 

 

93 cost more than 87 as the products used to make more octane cost more. Ditto 87 E-0 is more expensive than E-10 or E15 for the same reason. At least until alcohol subsidies disappear. It's way 100 octane race fuel sold a BP stations in our are are $10/gallon. 

 

 

 

 

Edited by Grumpy Bear
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Grumpy Bear
Grumpy Bear

https://www.consumerreports.org/fuel-economy-efficiency/top-tier-gasoline-worth-the-extra-price-a7682471234/   If it's on the list it's top tier even if the logo is not displayed.   

Black02Silverado
Black02Silverado

I use BP for the most part.  Basically because I get a discount using my BP card. But now that I can get E85. I is it in my 2019 Silverado 6.2. When I don’t. I notice a difference in performance. I al

txab
txab

I was partnered in a Texaco full service station from the early 80's to the early 90's. One thing that we knew about with other fuel dispensing locations, primarily small operations with only a few lo

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Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted (edited)

Gasoline is broad cut and defined by regulation by it's 10% and 90% temperatures and it's RVP (Reid Vapor Pressure) and, of course, it's octane rating. May also have some mandated components by law. 

 

For giggles notice that JP4 jet fuel covers allot of the gasoline range as do heavy and light naphtha. Even Kerosine! How many hydrocarbons do you think are covered in a temperature span between 86 F (IBP) and 392 F (FBP)? Look up the boiling points of as many C4 to C12 hydrocarbons as you care to before you tire for the search.( Do you know your law of "partial pressures and it's influence on RVP? On IBP and FBP?) You will need to, to understand how butane can be in a liquid with an IPB of 75 F when butane, the lightest feed stream in gasoline has a boiling point of 31 F and dodecane (boiling point about 420F)  in a fluid with a 392 F end point. 

 

It is allot of different molecules and there is no such thing as a 'Clean" cut in a heavy ends column. 

 

C7H16 Heptane and C8H18 Octane are only two component and roughly mid scale. 

 

https://www.engineeringtoolbox.com/hydrocarbon-boiling-melting-flash-autoignition-point-density-gravity-molweight-d_1966.html

 

See how many you can find of each group between those to carbon lengths. (link provided) 

 

 

 

 

 

Assessing the Feasibility of a Progressive Distillation Scheme

 

 

Edited by Grumpy Bear
Atlas Senior Enthusiast

Atlas

Posted
Posted

Top Tier Diesel?

 

GM recommends the use of Top Tier diesel in its diesel engines. If that's not available (which, it's not, around here) they recommend AcDelco branded fuel conditioner to be added to each tank. That stuff is unobtanium, so I'm not really sure what the risk is by running regular diesel from a busy fill station. For other diesels I've owned, I haven't paid any attention to additives or making sure I find top tier diesel. I buy fuel. The truck uses it. And I change fuel filters a little ahead of schedule, just to be extra safe. And that's it. Never had one that's been hard to start, not even in cold.

Atlas Senior Enthusiast

Atlas

Posted
Posted
8 hours ago, txab said:

No Costco around you?

 

Three of them. According to the official Top Tier website, none of the Costcos in our area sell Top Tier diesel. They sell Top Tier gasoline only. Two Costcos farther out (25+ miles away, in directions I don't regularly travel) sell Top Tier diesel but that's it. None of the local Chevrons, Shells, 76's, Cenex, Sinclair, Texaco, or store brand (Safeway, Fred Meyer) stations sell top tier diesel either.

 

In case anyone wanted to see if their local stations sell Top Tier gas/diesel:

https://www.toptiergas.com/fuel-stations/

  • Like 1
customboss Senior Enthusiast

customboss

Posted
Posted (edited)
5 hours ago, Atlas said:

 

Three of them. According to the official Top Tier website, none of the Costcos in our area sell Top Tier diesel. They sell Top Tier gasoline only. Two Costcos farther out (25+ miles away, in directions I don't regularly travel) sell Top Tier diesel but that's it. None of the local Chevrons, Shells, 76's, Cenex, Sinclair, Texaco, or store brand (Safeway, Fred Meyer) stations sell top tier diesel either.

 

In case anyone wanted to see if their local stations sell Top Tier gas/diesel:

https://www.toptiergas.com/fuel-stations/

Remember that Top Tier is a measure of deposits remaining. 
Grumpy’s excellent  treatise on his experience being a solvent control room blender and QC lab of same MISSES  the point of the Top Tier qualification.
 

The final marketed to us fuel product, gasoline or diesel, in the US, is poor performing low octane , low cetane fuels UNLESS you add POLYMERIC DISPERSANTS( marketed  as DETERGENTS ) and octane and cetane boosters.  
 

In simple terms our baseline non TOP TIER fuels are crap. 
 

 

Edited by customboss
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revrnd Senior Enthusiast

revrnd

Posted
Posted
5 hours ago, Atlas said:

 

Three of them. According to the official Top Tier website, none of the Costcos in our area sell Top Tier diesel. They sell Top Tier gasoline only. Two Costcos farther out (25+ miles away, in directions I don't regularly travel) sell Top Tier diesel but that's it. None of the local Chevrons, Shells, 76's, Cenex, Sinclair, Texaco, or store brand (Safeway, Fred Meyer) stations sell top tier diesel either.

 

In case anyone wanted to see if their local stations sell Top Tier gas/diesel:

https://www.toptiergas.com/fuel-stations/

Im not sure how accurate that site isScreenshot_20250901_151005_Chrome.thumb.jpg.c08d72586d6a9eeb7c9899e2d331ef44.jpg

 

That station switched to Esso (Exxon in Canada) a couple of years ago.

Jus Cruisin Enthusiast

Jus Cruisin

Posted
Posted
On 8/31/2025 at 10:02 AM, Atlas said:

Top Tier Diesel?

 

GM recommends the use of Top Tier diesel in its diesel engines. If that's not available (which, it's not, around here) they recommend AcDelco branded fuel conditioner to be added to each tank. That stuff is unobtanium, so I'm not really sure what the risk is by running regular diesel from a busy fill station. For other diesels I've owned, I haven't paid any attention to additives or making sure I find top tier diesel. I buy fuel. The truck uses it. And I change fuel filters a little ahead of schedule, just to be extra safe. And that's it. Never had one that's been hard to start, not even in cold.

I have never paid attention to "top tier". I buy gas and diesel from busy stations around me and I've never had fuel issues. 

  • Like 1
revrnd Senior Enthusiast

revrnd

Posted
Posted
8 minutes ago, Jus Cruisin said:

I have never paid attention to "top tier". I buy gas and diesel from busy stations around me and I've never had fuel issues. 

I know my brother used to use the Stanadyne additive. Not sure if he still does or not. He's had D'maxes in the GMT800, K2XX models & is on his 2nd T1XX truck.

Atlas Senior Enthusiast

Atlas

Posted
Posted
18 hours ago, revrnd said:

Im not sure how accurate that site is

 

That station switched to Esso (Exxon in Canada) a couple of years ago.

 

I'm not sure how accurate it is, either. But, it is the official site put out there by the organization that heads up Top Tier.

  • Like 1
revrnd Senior Enthusiast

revrnd

Posted
Posted (edited)
2 hours ago, txab said:

They do have ways of submitting info to them about stations

 

I contacted Top Tier via their website to tell them that the Mr Gas brand disappeared and is now owned by an Esso retailer.

Edited by revrnd
  • Like 2
revrnd Senior Enthusiast

revrnd

Posted
Posted

They replied yesterday and the locations were removed.

  • Like 1
revrnd Senior Enthusiast

revrnd

Posted
Posted (edited)

Also, according to Google, Petro Canada, Shell and Co-op Fuels are Top Tier. I occasionally fuel up @ the 1st 2 brands & dont recall ever see any Top Tier decals on the pumps.

Edited by revrnd
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