Does Premium Gasoline Have More Energy Than Regular?

[whizbyu]

Comparing my 2 cars:

2002 Lexus LS430 4.3 liter V8 SUL makes 290 HP, 10.5:1 compression ratio. 67 HP/liter
2024 Honda Civic 2.0 liter L4 RUL makes 158 HP, 10.8:1 compression ratio. 79 HP/ liter
My neighbor's car: 2024 VW Atlas w/ a 2.0 liter RUL turbocharged L4 makes 269 HP. 135 HP/liter
I've always understood that IN GENERAL, the more horsepower per liter a car engine makes, the shorter its lifespan. Translates to more heat production, more wear on the motors' internals, etc. When I look at the 3 cars I listed, it makes no sense why the Lexus requires SUL, when it makes the least power per liter and the compression ratio isn't higher than the Civic's.
Help me understand. I'm sure it is not THAT simple.

 

[RDY4WAR]

So you originally asked about energy per volume, but the equivalence is in mass. If by volume, premium has more energy per unit volume because of the higher density. But @RDY4WAR 's chart shows premium as being lower density, so I guess that point isn't clear.

However, unless I'm mistaken, isn't the overwhelming majority of the energy in gasoline in the hydrogen bonds? @RDY4WAR 's chart also shows a higher ratio of H to C in premium, which would mean more energy per unit.

The other possibility is that I'm being stupid about all of this, so feel free to dismiss this post as a semi-technical half-thought.

I know this post is old... but those vary (sometimes significantly) from one batch to another, especially when comparing winter and summer blends. The values for H:C and HoC are "the same" within MoE. The density, stoich, HoC, HoV, H:C, etc... is essentially the same. The higher octane just resists pre-ignition better. That's about it.

 

[Speedy3861]

This may or may not be relevant, however, when I had my 2019 Honda Touring Coupe with 1.5t engine/CVT there was an ongoing discussion on the CivicX forum about using 93 octane fuel as a cure-all for many things. My Civic was stock, no tuning or mods and I'm meticulous about tire pressure, maintenance and record keeping. This is a totally non- scientific study controlling as many variables as I could. Running Mobil1 0w20 AFE 5k OCI's and Honda filters. All fuel from 1 single Shell station with Toptier stickers prominently displayed, all fuel dispensed from one pump. I keep meticulous mpg records at each fill-up.(always have, it's an OCD thing) ran 30 days in June on 87 octane, then 30 days in July on 93. Miles were accumulated commuting essentially the same route and travel conditions.
Significant results:
My credit card bill was significantly higher for July
Subjectively car ran perceptible smoother
Idle seemed to be somewhat quieter
Computed MPG actually decreased by a bit less than 1 mpg using the 93 octane
Conclusion: total waste of time and money, car runs perfectly on Toptier 87.
It's a small-displacement Turbocharged DI engine and at 27 000 miles my Honda Master-Certified Technician looked down into one cylinder with a snake camera and found literally no carbon deposits.
His only comment was to keep using Toptier 87 and don't worry about it, Hondas run just fine on 87.

 

[hank2]

I've owned a number of cars that had substantial improvements in fuel mileage when using premium fuel long term. Actually, that was most evident on several '90's and a 2001 Nissan. All three spec'd 87 PO. Dealer advised premium on all three. Some vehicles had/have wider parameter spark advance than others. On those vehicles, if it stays out of the knock sensor rollback on advance, it will reward with more power and mileage. I just have the feeling that that may not be the case any longer. I have never understood the thinking of many turbo or ultra-high compression DI vehicle owners that insist on using 87 in an engine that requires or strongly recommends 91-93.

 

[Triple_Se7en]

We use 93 octane because it contains more detergents and burns more evenly.
The 'Evenly' thing translates best in our two vehicles when we slow down for a turn at an intersection and when turned, accelerate back to the speed limit.
The Premium 93 octane fuel allows our engines to go thru this process without any hesitation in the engine (hesitation = 87 octane). There's no need to use passing gear to obtain the increased speed limit number quicker.

If it weren't for more detergents and this Evenly thing, I would never pay 80 cents to $1.00 more per gallon for it. If I wanted Premium for just increased detergents, I would load up on Techron Concentrate Fuel Treatment and buy it by the case on sale. That would be much cheaper using this treatment monthly.... every 2nd fill-up. (for 15-17 gallons or-so fuel tank.

 

[D1sc]

This may or may not be relevant, however, when I had my 2019 Honda Touring Coupe with 1.5t engine/CVT there was an ongoing discussion on the CivicX forum about using 93 octane fuel as a cure-all for many things. My Civic was stock, no tuning or mods and I'm meticulous about tire pressure, maintenance and record keeping. This is a totally non- scientific study controlling as many variables as I could. Running Mobil1 0w20 AFE 5k OCI's and Honda filters. All fuel from 1 single Shell station with Toptier stickers prominently displayed, all fuel dispensed from one pump. I keep meticulous mpg records at each fill-up.(always have, it's an OCD thing) ran 30 days in June on 87 octane, then 30 days in July on 93. Miles were accumulated commuting essentially the same route and travel conditions.
Significant results:
My credit card bill was significantly higher for July
Subjectively car ran perceptible smoother
Idle seemed to be somewhat quieter
Computed MPG actually decreased by a bit less than 1 mpg using the 93 octane
Conclusion: total waste of time and money, car runs perfectly on Toptier 87.
It's a small-displacement Turbocharged DI engine and at 27 000 miles my Honda Master-Certified Technician looked down into one cylinder with a snake camera and found literally no carbon deposits.
His only comment was to keep using Toptier 87 and don't worry about it, Hondas run just fine on 87.

I've owned a number of cars that had substantial improvements in fuel mileage when using premium fuel long term. Actually, that was most evident on several '90's and a 2001 Nissan. All three spec'd 87 PO. Dealer advised premium on all three. Some vehicles had/have wider parameter spark advance than others. On those vehicles, if it stays out of the knock sensor rollback on advance, it will reward with more power and mileage. I just have the feeling that that may not be the case any longer. I have never understood the thinking of many turbo or ultra-high compression DI vehicle owners that insist on using 87 in an engine that requires or strongly recommends 91-93.

Listen to your tuner and if he doesn’t mess with the knock sensors and uses meth injection the octane is negotiable.IATs rule the dyno.

 

[LowMilesLesabre]

Hmmm. I wonder if whether the OP’s question about higher energy in premium gasoline might be due to an inference because he is associating premium fuel with octane ratings? I’m asking this because for SOME premium gasoline, they. ‘can’ have higher energy if they are ethanol, free fuels. Many times, though not always, if you have an option for ethanol free gasoline, it is more likely than not to be the premium grade, which also has the higher octane rating. Perhaps the OP has heard of people getting better MPG with premium fuels, and mistaking this result due to the octane rating when in fact, it was because the fuel had no ethanol. Here in southern Ontario, ethanol, free fuels are no longer marketed in large metropolitan areas, and so, for example, our Shell V Power now can contain up to 10% ethanol, which it did not as of several months ago. And so I am not. surprised that my fuel mileage is now lower using premium than it was before. It’s easy for any of us to observe something and deduce the cause when in fact, it is a correlation and not a causation.

 

[RCF71]

New guy here, but have lurked on and off over the years. Chemical engineer by degree, car/truck enthusiast, with many years in refining including economic optimization/blending of gasoline (some of my favorite, but often most stressful, jobs).

Just read through this thread and a lot of good info, but some not as good. No offense intended to anyone above, so please don’t read that much into it. I’ll add a few bullet points (not gonna write a thesis)…

- Premium may or may not have more energy than regular. Depends on the refinery, what crude oil they run, what units they have, econs between gasoline/jet/diesel, and market area in terms of what components and how much of each are available for their gasoline blending.

- In general, the ethanol content will be the same for quality testing purposes, so not really ethanol dependent as far as the production of the base gasoline. More/less ethanol may be added (within an allowable range) when a truck is loaded to supply retail depending on economics, but this is AFTER the gasoline has been produced.

- The website quoted above (Intelligenthq.com) is pretty unintelligent about gasoline.

- The table of qualities (not specs) posted is ONE good sample of each, not representative in general (see first bullet point). Specs are min, max or ranges with min/max. Actual qualities can vary quite a bit and still meet specifications.

- Non-ethanol/Ethanol free does NOT mean it’s pure gasoline. For example, isobutanol is used in a lot of that “grade” of gasoline. So you can’t assume how much more energy dense it might be.

- Pump labels are MINIMUMS. For example, one post mentioned E15 with an 88 octane pump label giving better results than the 89 octane “up to 10% ethanol” midgrade. This could be an example of actual being better than the pump label. Not saying thats the only reason, but it could be.

- Refiners don’t use additives to boost octane. Gasoline is a complex blend of many different streams, some have octane as low as ~60 and some are 100+. So changing octane is not a matter of some small volume of additive but rather larger volumes of individual streams, so yes it can affect the energy content.

- Premium gasoline does not necessarily have more addtives/detergents. All gasoline has to meet certain specifications, but some gasolines (Top Tier for example) exceed those specifications.

Thats all I can think of for the moment.

 

[350Rocket]

Actually for most folks running rug on an engine requiring premium it takes many years until a rebuild would be required and in the case of one of my cars the engine is $99 at the wrecker.

Get yourself some inexpensive equipment and measure knock, on my Volt at 1500’ elevation 88e15 isn’t significantly more knock than premium.

Unless your running a turbo and a tune going to the track or towing up mountains in the desert it’s unlikely any of what you describe is going to happen.

Its rare an average vehicle on the road benefits from premium.

I see a very tiny difference in knock retard when I briefly run 91 in my 05 Silverado with 258k miles.... using torque pro the monitor...no audible signs of knock. I run 91 e0 in all my outdoor power equipment though. They take a lot less fuel than my truck or car.

 

[350Rocket]

I haven't seen this come up yet in the 4 pages so far ...seems we're only discussing whether higher or lower octane has any effects except resistance to knock.... but all the gas stations I go to advertise much higher levels of detergents in their 91 octane. Any information out there on this or would it possible to discuss? Since for many people (who don't need higher octane) this would be the main difference from regular to premium.

 

[vpr5703]

I haven't seen this come up yet in the 4 pages so far ...seems we're only discussing whether higher or lower octane has any effects except resistance to knock.... but all the gas stations I go to advertise much higher levels of detergents in their 91 octane. Any information out there on this or would it possible to discuss? Since for many people (who don't need higher octane) this would be the main difference from regular to premium.

If this is all you're after just throw in a bottle of Chevron Techron in every now and again. It'll be cheaper than running premium by far.

 

[supton]

Comparing my 2 cars:

2002 Lexus LS430 4.3 liter V8 SUL makes 290 HP, 10.5:1 compression ratio. 67 HP/liter
2024 Honda Civic 2.0 liter L4 RUL makes 158 HP, 10.8:1 compression ratio. 79 HP/ liter
My neighbor's car: 2024 VW Atlas w/ a 2.0 liter RUL turbocharged L4 makes 269 HP. 135 HP/liter
I've always understood that IN GENERAL, the more horsepower per liter a car engine makes, the shorter its lifespan. Translates to more heat production, more wear on the motors' internals, etc. When I look at the 3 cars I listed, it makes no sense why the Lexus requires SUL, when it makes the least power per liter and the compression ratio isn't higher than the Civic's.
Help me understand. I'm sure it is not THAT simple.

2002 and 2024, that is a good 22 years of difference.

I'm not sure, would assume that in 2002 Lexus was using VVT. But still, I suspect today "most" are using some level of Atkinson to boost mpg, holding the intake valve open a bit longer to bleed some of the intake charge off and lower peak cylinder pressure, thus allowing low octane gas and avoiding ping. When not on the throttle.

I also suspect that direct injection comes into play here, gas is injected at nearly the last second, thus it's harder to have pre-ignition.

 

[350Rocket]

If this is all you're after just throw in a bottle of Chevron Techron in every now and again. It'll be cheaper than running premium by far.

That's what I have been doing (with gumout regane - we don't have chevron easily available in Canada) but it's $15 a dose so I was actually curious about the numbers. How much extra pea in 91 vs 87, cost of dose vs that.

 

[RCF71]

If this is all you're after just throw in a bottle of Chevron Techron in every now and again. It'll be cheaper than running premium by far.

Exactly what I practice and recommend!

 

[350Rocket]

Exactly what I practice and recommend!

Based on my math and prices I've seen recently it would cost about $18 more to use 91 instead of 87...so I would imagine it has to be a better bargain to add separately....but I'm still curious about the dosage of detergents, specifically between Esso/Exxon top tier 87 and top tier 91 or shell. My employer supplies a gas card (Esso) for my work fuel. I have to put in enough to cover my own usage and I occasionally go with shell just in case there are additive differences.

I usually just dump a full bottle of gumout aio or the high mileage regane...but I probably only do that a few times a year. I could also use smaller doses more frequently, or even smaller doses at every tank, which could be similar to using premium every tank just without the higher octane. Unfortunately I haven't seen any discussion on what actual differences are.

 

[Speedy3861]

If you read the information on the Toptier website, apparently there's enough difference just with the Toptier additive package to make additional cleaners either redundant or unnecessary, 87 or 93. Apparently BP has an additive package that supposedly exceeds Toptier, they used to be Toptier listed and go into some detail on their website (without specifics, of course) about their additive package. They probably do, but probably don't want to pay the Toptier licensing fee.

 

[350Rocket]

I looked at esso, shell and Petro Canada. They basically all claim higher detergents in their 91+ but no information on the actual difference that I could see.
I attached screenshots of what they said about their premium.

 

[SHOZ]

I would think the more additives the less btus.

 

[michael007]

I looked at esso, shell and Petro Canada. They basically all claim higher detergents in their 91+ but no information on the actual difference that I could see.
I attached screenshots of what they said about their premium.

This post show's what Chevron does (or used to do as the info might be outdated)

https://bobistheoilguy.com/forums/threads/is-it-confirmed-if-chevron-supreme-gas-has-more-techron-additive.372901/post-6605678

 

[Burt]

It isn't true that regular and premium gasoline have the same energy content per gallon. Gasoline is a mixture of various components to achieve the desired octane. Generally speaking, there is an inverse relationship between octane and energy content:

Ethanol is 76,000 btu per gallon and 109 octane
Butane is 130,000 btu per gallon and 94 octane
Natural gasoline is 137,000 btu per gallon and 70 octane

All of the above components plus pentane, hexane etc are present in modern day gasoline.

This is why premium (high octane) gas tends to have lower btu per gallon. This can offset some of the efficiency gains from higher compression and more advanced ignition timing. Gasoline can have anywhere between 114,000 and 125,000 btu per gallon.

Disclosure: I used to analyze and develop natural gas liquids processing plants and we were very aware of the btu content of the products we sold to refineries.