Octane level and performance

[Mark_888]

Where did you see in my post such a thing? Are you blind or having some kind of visual illusions? I just posted a link of a very recent and interesting article about Premium Gas Consumption in USA.

Not blind. But what value is it for them to test a few engines and then start extrapolating that to ALL engines? IMO, it is reckless for them write stuff like that.

 

[need4spd]

Mark 888

Unfortunately you missed the point of my post which was in reply to the OP discussing if there were any benifits in using premium in their 3.8 V6, they were not asking about the 5.0 V8 (which they do not own) and where it is a known fact that premium in the V8 produces more HP.

I clearly said:

" I remember reading that Consumer Reports did a study just recently (again) and found that there was no difference in gas mileage putting premium in a car rated for regular unleaded, even the EPA came out with a statement about that."

While my source was incorrect, as it was AAA (thanks to the other poster) that recently stated this, the information is that a Car designed to run on regular unleaded does not improve in HP or MPG when premium is used, and they used dynometers and repeatable test conditions in testing.

Driving one day to the next on the same road has many other factors involved, so it is hard for the average consumer to do that comparison without testing on a dynometer as I had said.

I never disputed that the V8 Genesis performs differently on one grade verses the other grade of gas, and in fact said it does based on design of the mapping of the engine to retard knock when operating on regular (it reduces output as timing is retarded to eliminate the knocking on 87 and as a result a slight loss in performance). When running on premium gas, as it is designed to, it makes full rated output as its design is to have higher compression, and run properly (without knocking) on premium gas. On regular, retarding the timing reduces power and eliminates the knocking with 87 octane gas.

Also, you should check what octane really means, it is a rating for the gasoline to be able to compress more before self exploding in a cylinder, not a value of energy content of the gasoline. A grade of 87 means that it contains 87% octane in it and 13% of other equal energy content types of combustible gases in it. Similarly, 93 means 93% octane fuel in it and 7% of other combustible gases, raising the point of compression or these gases before it self explodes in the cylinder.

Octane is just a combustible gas that has 8 carbon atoms and requires a lot more pressure (compression) before it self ignites. Octane is more expensive than other explosives gases, so you pay more when the percentage of Octane is higher.

Higher compression ratios in engines allow for more HP to be produced in the same size engine, so if you are able to compress the gas more, you can produce more HP with the use of premium fuel.

Using 100 octane in race cars is so that they can bump up the compression ratio in their engines to squeeze all the HP out of them without early auto ignition (and the resulting damaging knocking).

 

[GCyr42]

They didn't test Genesis engines. Are you saying that the Genesis V8 doesn't get better MPG with premium?

Did you expect that they would test every available engine? It says to use what the manufacturer recommends. If that's premium, then use it! Otherwise, you're wasting your money which is fine with me because it isn't my money.

 

[Mark_888]

Did you expect that they would test every available engine? It says to use what the manufacturer recommends. If that's premium, then use it! Otherwise, you're wasting your money which is fine with me because it isn't my money.

1. If they don't test every engine, then they can't make any inferences or assumptions about engines they didn't test. It is a proven fact that the Genesis V8 gets higher HP and better MPG with premium, but it can run on regular (which many owners do), so the idea that ALL engines only are optimized for a singe octane level is FALSE.

2. Hyundai recommends premium on the Genesis V8, but they say it runs fine on regular (with lower HP and lower MPG). Many Genesis V8 owners on this forum have said they use regular with no problems. So your comments about "manufacturer recommendations" don't seem to apply.

3. They didn't test mid-grade gasoline, which a major flaw in their testing. I use a mid-grade on my V6 (actually slightly less octane than mid-grade with a blend of regular and premium) and I don't think I am wasting my money (slightly better HP and MPG).

4. Not all regular (or premium) gas is the same octane level. Regular in the US usually varies between 85 and 87 octane (depending on altitude, pollution controls, etc). Modern engines with electronic ignitions can adjust for the difference without retuning the ignition system, something that older cars cannot do.

 

[danygenesis]

Not blind. But what value is it for them to test a few engines and then start extrapolating that to ALL engines? IMO, it is reckless for them write stuff like that.

As reckless is for you to post here in this thread knowing that you don't own a 2G Genesis that doesn’t have the same engine as your pre GDI 1G Genesis.

 

[Mark_888]

As reckless is for you to post here in this thread knowing that you don't own a 2G Genesis that doesn’t have the same engine as your pre GDI 1G Genesis.

I have been clear that I have 1G Genesis V6 (pre-GDI). But I doubt that there is difference in the way it can handle different octane levels.

Both the pre-GDI V8, and the GDI V8 (since 2012) have increased HP with premium according to Hyundai. And since Hyundai submitted their EPA mileage ratings based on premium for both versions, I would assume that the V8 has always had better MPG using premium (unless we assume that Hyundai marketing people are complete idiots).

Also, if one reads the article you quoted carefully, they don't claim there is no difference in the engines they tested with regular and premium (not Genesis engines), they just say the differences are not "significant." They don't report the actual numbers, so they expect us to take their judgement on the issue. Also, they never tested mid-grade vs regular.

 

[glennk]

Has anyone compiled the numbers on Regular vs Premium? Is there a cost benefit to using Premium?

 

[danygenesis]

Has anyone compiled the numbers on Regular vs Premium? Is there a cost benefit to using Premium?

In my case not (2G 3.8) Premium cost is around 22-25% higher than Regular in South Florida and my consumption is at the most 1 MPG highway with Premium which is just 3-4% increase. Yearly will be $520 difference with current prices.

 

[Mark_888]

Has anyone compiled the numbers on Regular vs Premium? Is there a cost benefit to using Premium?

Depends on which engine you are talking about. There is a V6 and a V8.

I have the pre-GDI (pre 2012) V6 3.8L with regular fuel injection, and I got slightly better highway MPG with mid-grade, but did not improve any further with premium.

Each person should conduct their own testing to get actual results for their engine and driving conditions. But given that price of gas increases with higher octane, it is not likely to save any money with higher octane gas. But there may be some other benefits.

 

[Alwaysforward]

Has anyone compiled the numbers on Regular vs Premium? Is there a cost benefit to using Premium?

I have. Its within a few cents. Do a search for the post.

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[Crusty Old Shellback]

Not blind. But what value is it for them to test a few engines and then start extrapolating that to ALL engines? IMO, it is reckless for them write stuff like that.

So is there some new magical internal combustion engine that no other manufacture knows about besides Hyundai, that would cause their engine to operate differently from any other internal combustion engine that would require a test of every single internal combustion engine to extract the data that YOU would be happy with?

 

[Mark_888]

So is there some new magical internal combustion engine that no other manufacture knows about besides Hyundai, that would cause their engine to operate differently from any other internal combustion engine that would require a test of every single internal combustion engine to extract the data that YOU would be happy with?

They only tested 3 engines. If one wants to know about the Genesis engines, then why would someone want to test anything other than the Genesis 3.8L V6 or 5.0L V8? Doing a MPG test is not rocket science, and I am sure that members can do it themselves.

Hyundai tested the V8 and determined it got about 7 HP more premium. and it got better MPG (since they submitted their EPA mileage test using premium).

I don't think all other engines operate differently than the Genesis engines, but some probably do. The Genesis owners manual specifically says for the V8 that one can use regular, but that premium is recommended. How many other automakers allow that choice for their engines (as documented in their owner's manual)?

Even in the articles referenced above, they admitted that there were often differences in MPG with different octane, but they concluded it was not worth it (and didn't publish the details of their tests). Also, they never tested mid-grade. I found on my 1G V6 that going higher octane than mid-grade did not help MPG any further, but mid-grade was better MPG than regular. Each person can do their own testing and decide for themselves.

 

[Seejay]

As someone wrote on a Genesis coupe forum, the topic takes on a religious tone.

To the OP: Extrapolating from the v6 coupe engine (the sedan engine is tuned differently for more torque with a flatter curve), I would guess about 4 HP difference.

I so hated the way my Sonata 3.3L v6 ran on regular or mid grade, I never even tried those grades in the genesis. A friend in the refining industry advised me to always use premium with high compression engines and he does so as well. And i must admit, my experience has been trouble free when it comes to the fuel system. I have never put any kind of fuel conditioner in any of the cars that I have owned and the fuel systems are clean and trouble free. He stated that anything that is "off" (what chemical industry techs call "still bottoms") go into the regular gas, so when they add the "off" stuff, the gas is bad, and when they don't, the gas is good. Pardon me, but I really did not understand what he was saying. He also said the amount of additives and the quality of them are also a factor. And lastly, he said (big gas refiner with Spanish sounding name) refrains from putting any ethanol in their premium, at least here in south Texas. I think that is what makes most of the performance and mileage differences I perceive.

Knock sensor technology was developed for turbo charged engines in the mid 1980s--the first high compression engines since the 1960s. It was necessary because of the problems with knocking when the turbo spun up. It was later added to normally aspirated engines when manufacturers realized that more power could be obtained with high compression and knock sensors. All decent ECU/EFI engines will retard the spark when the knock sensor detects knocking. Most modern high compression engines deliver less mileage and performance when they run regular gas. It depends on how they are tuned and how "far" the engine designer wants to push things. So a manufacturer might "recommend" or "require" premium fuel, depending on the design.

On old Mercedes-Benz engines, you can see a user-adjustable calibrated static timing lever on the distributor in order to run regular gas when premium was not available. In the 1960s, premium was 100 octane. It was basically the 93 octane (R+M)/2 stuff we have now, with lead added to bump it to 100.

 

[GensisBoss]

IMO I think its better to put 91 just because it makes the engine run smoother but it wont hurt your car to run any other octane level

 

[Crusty Old Shellback]

I don't think all other engines operate differently than the Genesis engines, but some probably do. The Genesis owners manual specifically says for the V8 that one can use regular, but that premium is recommended. How many other automakers allow that choice for their engines (as documented in their owner's manual)?

In the last 15 years, I've bought 6 new cars/trucks and 3 new motorcycles from 5 different manufactures. Every one of them has a recommended fuel statement in their owners handbook.

I work in test and evaluation. You can't test every little thing or in this case engine. BUT, you can test a representative number of them and extrapolate from that. Plus you use past history as well to come to your conclusions.

So why do you continue to act as if Hyundai's are so much different from the rest of the world?

 

[Mark_888]

In the last 15 years, I've bought 6 new cars/trucks and 3 new motorcycles from 5 different manufactures. Every one of them has a recommended fuel statement in their owners handbook.

I work in test and evaluation. You can't test every little thing or in this case engine. BUT, you can test a representative number of them and extrapolate from that. Plus you use past history as well to come to your conclusions.

So why do you continue to act as if Hyundai's are so much different from the rest of the world?

1. I am quite aware of statistical sampling, both as part of my education and my professional work experience. Those tests published in the magazines were neither valid random statistical samples, nor was the "confidence" level sufficient enough (with a sample size of only 3) to have any scientific significance.

2. Hyundai says that premium is recommended for the Genesis V8, but regular can be used with less HP and lower MPG. That reinforces the idea that at least the V8 has sufficient flexibility to exploit different octane levels, with different results for each octane. This is a fact, even though that seems to contradict the findings of the magazine articles that engines are designed to use only one specific octane level.

3. I personally have tested my Genesis V6 (pre-GDI) and found that it gets better HP, better MPG (about 1 MPG better on the highway), and the engine runs quieter with mid-grade. I have not noticed any obvious improvement beyond using mid-grade (such as premium).

4. I made no judgements about the financial trade-off, due to the higher cost of purchasing more octane, only that the engine performance is different between regular and mid-grade on my Genesis engine. For many, even if the engine performed better with more octane, it might not be worth to them.

5. Beyond my own experience with my pre-GDI V6, I don't know for sure how other Genesis engines (or even other owners with same engine as mine) will perform with octane levels above regular. I have suggested that if people are interested, then they try it for themselves, rather than take the word of some magazine articles that lack full disclosure of their results, and are fundamentally flawed.