Does Premium Gasoline Have More Energy Than Regular?

[fnbrowning]

Question regarding automotive gasoline. Does premium gasoline have more energy per unit volume, than regular gasoline?
IMPORTANT: This is not an octane or anti-knock question.

Stated otherwise, in laboratory conditions with a single cylinder test motor of nominal compression; if the same amount of premium gasoline and regular gasoline is burned, which would produce more work? HP or Joules, etc.

A link to any articles of energy content of different gasoline grades or tests or fuels would be sincerely appreciated!

 

[Astro14]

No. It does not.

The advantage of higher octane is the ability to run higher compression, or greater boost, which yields more HP.

But with modest compression, in a normally aspirated engine, there is no advantage.

The fuel has the same energy content because the fuel itself is basically the same. The additives themselves have little energy content.

 

[javacontour]

First, define premium and then we can answer your question.

 

[kschachn]

Nope it does not, in and by the octane rating itself. There are multiple ways to increase the rating however, other than just the branching of the octane molecule itself.

However if your engine can advance the timing due to the higher rating (or be designed with a higher compression ratio) then more of the available energy from the gasoline can be extracted.

But in general the energy content is the same since this is dictated by the bonds in the molecule. It also has the same burn speed, flame temperature and all the other things that people imagine about higher octane gasolines.

I don’t know what else premium gasoline means other than a higher octane rating. You say your question isn’t about that but what is it then?

 

[D1sc]

The rumor I grew up with was higher octane burns slower thus allowing a higher compression ratio. All the science behind the effects of elevation changes forced induction methanol injection ect. I’ll leave to google or ask someone who has to keep up with current technology any engine builder.

 

[kschachn]

The rumor I grew up with was higher octane burns slower thus allowing a higher compression ratio. All the science behind the effects of elevation changes forced induction methanol injection ect. I’ll leave to google or ask someone who has to keep up with current technology any engine builder.

No it does not burn slower. It resists ignition by sources other than the spark plug. That’s a function of the octane molecule morphology.

 

[Zee09]

Yeah, that's why they call it premium

 

[dubber09]

this article would suggest higher octane fuel burns slower:

https://www.motortrend.com/how-to/combustion-basics-how-does-fuel-make-a-difference/#:~:text=Fuel%20with%20an%2087%20octane,the%20burn%20rate%20is%20slower.

while this one suggests it burns more evenly:

MIT School of Engineering | » What’s the difference between premium-grade and regular gasoline?

engineering.mit.edu

imho mid grade octane gas is beneficial to GDI and TGDI engines as it helps prevent pre-ignition and engines will run smoother while high octane gas may result in greater carbon deposits.

 

[ammolab]

this article would suggest higher octane fuel burns slower:

https://www.motortrend.com/how-to/combustion-basics-how-does-fuel-make-a-difference/#:~:text=Fuel%20with%20an%2087%20octane,the%20burn%20rate%20is%20slower.

while this one suggests it burns more evenly:

MIT School of Engineering | » What’s the difference between premium-grade and regular gasoline?

engineering.mit.edu

imho mid grade octane gas is beneficial to GDI and TGDI engines as it helps prevent pre-ignition and engines will run smoother while high octane gas may result in greater carbon deposits.

Why would high octane leave more carbon deposits? There can’t be more carbon there. Where is scientific evidence..testing or research results showing this. There are engines that run high octane fuel their entire life without any woes from carbon deposits.
This has to be urban, no moterhead legend

 

[kschachn]

this article would suggest higher octane fuel burns slower:

https://www.motortrend.com/how-to/combustion-basics-how-does-fuel-make-a-difference/#:~:text=Fuel%20with%20an%2087%20octane,the%20burn%20rate%20is%20slower.

while this one suggests it burns more evenly:

MIT School of Engineering | » What’s the difference between premium-grade and regular gasoline?

engineering.mit.edu

imho mid grade octane gas is beneficial to GDI and TGDI engines as it helps prevent pre-ignition and engines will run smoother while high octane gas may result in greater carbon deposits.

Yeah I've seen that Motortrend article before. Thanks but I will stick to the body of technical knowledge that understands chemistry and combustion a little bit better. And that MIT article seems to equate "evenly" with resisting premature ignition, when they say "and burns more evenly than lower-octane fuel under harsh conditions, resisting detonation and knocking." Not more "even" in terms of more complete combustion.

Do GDI and TGDI have a problem with pre-ignition? I haven't heard of that as a global issue with those engines.

 

[BMWTurboDzl]

Question regarding automotive gasoline. Does premium gasoline have more energy per unit volume, than regular gasoline?
IMPORTANT: This is not an octane or anti-knock question.

Stated otherwise, in laboratory conditions with a single cylinder test motor of nominal compression; if the same amount of premium gasoline and regular gasoline is burned, which would produce more work? HP or Joules, etc.

A link to any articles of energy content of different gasoline grades or tests or fuels would be sincerely appreciated!

In laboratory conditions per unit of volume in terms of BTU's the answer should be no because, typically, there is ever slightly more additive mixed in with premium gasoline vs regular. I'm talking extremely small differences in the amount of additive. Think a couple of centiliters per gallon. I don't know how that translates into BTU's, but I'd imagine it's not very much being that 1 gal of gasoline contains 125,000 Btu.

 

[KCJeep]

I run premium for the detergents mostly. The Mustang is already faster than any Maverick.

 

[Zee09]

I run premium for the detergents mostly. The Mustang is already faster than any Maverick.

When turbos spool
Electric rules...

 

[kschachn]

As @javacontour notes we need the OP to come back and define premium.

 

[javacontour]

I don’t know what else premium gasoline means other than a higher octane rating. You say your question isn’t about that but what is it then?

This is why I asked.

Premium is such a vague term as to almost be meaningless.

 

[twX]

I've seen one study showing better engine efficiency with lower octane fuel, in an engine designed for the lower octane fuel, but this is something that might not apply to the fuel from your local refinery.

If you wanted to test the efficiency of two different fuels, you could compare MAF sensor readings at warm idle with both fuels in the same conditions. As long as the fuels have the same ethanol content, the more efficient fuel probably has more energy or higher flame speed.

 

[kschachn]

If you wanted to test the efficiency of two different fuels, you could compare MAF sensor readings at warm idle with both fuels in the same conditions. As long as the fuels have the same ethanol content, the more efficient fuel probably has more energy or higher flame speed.

I don't understand that part about efficiency?

 

[fnbrowning]

As @javacontour notes we need the OP to come back and define premium.

Premium is defined as 91 to 100 octane fuel. Regular is defined as 87 octane fuel. Assume that the only difference between the fuels is the octane MON or RON is rising due to refining or common approved additives. No ethanol in this discussion. Pure gasoline only.

> There are statements made elsewhere that as more octane is added to reduce spark knock, the specific gravity and energy content of the fuel per unit of weight are reduced. The allegation being made is that to make a given amount of power in the same simple purpose-built test engine, more high-octane fuel must be burned in the engine than regular octane fuel.

True or False?

 

[dnewton3]

Do GDI and TGDI have a problem with pre-ignition? I haven't heard of that as a global issue with those engines.

Isn't that the crux of the LSPI (low-speed pre-ignition) issue? I'm not saying it is; I'm asking if it is. If so, I would say they are essentially the same topic, but maybe induced by different means.

 

[kschachn]

Premium is defined as 91 to 100 octane fuel. Regular is defined as 87 octane fuel. There are statements made elsewhere that as octane increases, the specific gravity and energy content of the fuel per unit of weight are reduced. The allegation being made is that to make a given amount of power in the same simple test pony motor, more high-octane fuel must be burned in the engine than regular octane fuel.

True or False?

False on all of that. Again though it depends on how the octane rating is achieved. Once you are using an adjunct such as EtOH then you are also changing fundamental properties of the gasoline as expressed as a majority C-8 mixture.

The second part of your statement isn't true either. If the compression ratio stays the same as well as the ignition timing then a higher octane fuel will give the same power as a lower octane one. If the compression is increased or the timing advanced, then a higher octane fuel will be more efficient and yields more power per gram.

Don't confuse all of this with race fuels. I thought of that given your mention of 100 octane. Race fuels can be comprised of many compounds all of which do in fact change the combustion temperature, flame speed and other properties.