Benefits of running premium...

[Grench]

To my somewhat dated knowledge... In a somewhat random order.

All gasoline is the same when it leaves the main pump at the terminal. In the business it is commonly called, "87 no lead." There three or more pumps at the terminal, depending on local regulations. Each has a different blending stock.

The octane value has no relevance to the amount of combustive power present in the mixture.

Blending octane value (BOV) winds up being important. A 5,000 gallon truck may fill up 90% with "87 no lead" BOV 87 and 10% with EtOH (Ethyl Alcohol) BOV 108 (round numbers) resulting in a (9*87 + 108)/10 = 89 octane Ethanol blend.

Typically this mixing is done in the truck on it's way from the depot to the station. Slosh/difusion.

There are over 10,000 identifiable components within any pump acquired standard gasoline. The "Octane" rating is based on a bench sample of Ocatane and Heptane as a benchmark. You will never get this at the pump.

Between tar and methane there are thousands of possible hydrocarbon combinations, particularly if you start dealing with left & right handed molecules, etc... Acetylene is probably the most ideal power to weight. Because of this it is expensive and refined out of pump gas.

Pump gas is composed of materials that are not saleable by themselves. This resultant blend of junk is then 'adjusted' to fit automotive requirements by adding good stuff until the vat of leftovers / not-so-good stuff meets minimal federal & state requirements.

Octane is one measurement, vapor pressure is another, calories is yet another, then there is the distillation curve showing how much of the fuel evaporates at what rate when heated at a constant rate.... etc...

Oil companies don't like Ethanol primarily because it is not 'pipeline fungible.' It mixes with water and pulls the water with it. So, a 200 proof (100%) ethanol stream will come out the other end with the water it picked up along the way increasing volume and decreasing usability. Ethanol + water + gasoline = cloudy gas.

MTBE & ETBE have BOV in the 116 range. MTBE was removed due to some issues with leaky tanks and water tables. ETBE never fully took off.

YMMV...

 

[CJF]

They both say essentially the same thing?

Explanation in #34 is pre-spark explosion, rather than the #26 explanation of spark initiated explosion. (Part of the air-fuel mixture explodes before the spark initiated flame front gets there.) From my digging around, true pre-spark "knock" is supposedly much less common, and even more damaging than spark initiated "pinging".

 

[FirstToy]

higher octane gas is simply harder to ignite/ more difficult to burn. That is it. It isn't "better gas".

Additives are probably more important but you get that in low octane as well (from Chevron for example).

 

[CJF]

Octane is one measurement, vapor pressure is another, calories is yet another...

No wonder my Land Cruiser's so fat!

 

[Grench]

Continued... More thoughts on the subject. My opinions only.

Aditives are drops in the proverbial bucket. They can be somewhat effective at preventing crystalization of ethers in a blended oxygenate (DOGI100 or the like), but otherwise they're pretty much adding more of things that are already present. The only effective additive at improving engine performance was lead. Do not put lead in your trucks. Nasty stuff really and it will eat your cats.

If your truck runs on 87 no lead it will receive no performance gain from a higher octane pump fuel... As a general statement. If you increase the compression ratio then you will likely need to increase the octane of the fuel to prevent early detonation. See supercharger/turbo.

Important fuel rule #1. Never ever under any circumstances fill up while the fuel delivery truck is in the station. If you can, avoid filling up at a station for the next 30 minutes after the truck leaves. When they drop of fuel it stirs up the sediment and water that sits in the bottom of the tank into solution. You can literally wind up filling your gas tank with 1/8 water 7/8 gas, drive 2 miles then it will die as the water settles out to your tank's pickup.

YMMV.

 

[lowbanks]

I remember a similiar discussion when I belonged to a Previa group (boy I miss that van).
Someone stated that octane was like shoe size.
If you're a size 9, then wearing a size 12 (although you could manage), will not make you run faster.

Someone also calculated that the price difference(regular vs premium) over many, many years or mileage, you could almost buy a new engine (or other toys).