regular unleaded or super?

[Madhornet 18]

I have a 2009 3.8 Genesis sedan black 91k. I have been using supreme unleaded if I am saying it right for a year. I have read many comments and trying to inquire from dealers. Is regular unleaded purfered for the 3.8? My gas mileage is not great with supreme nor does it accelerate smoothly like when I first got it. I have only had it for 2 years purchased "used" love it. I just need to know is regular unleaded best for the 3.8 sedan?

 

[homeofstone]

I have a 2009 3.8 Genesis sedan black 91k. I have been using supreme unleaded if I am saying it right for a year. I have read many comments and trying to inquire from dealers. Is regular unleaded purfered for the 3.8? My gas mileage is not great with supreme nor does it accelerate smoothly like when I first got it. I have only had it for 2 years purchased "used" love it. I just need to know is regular unleaded best for the 3.8 sedan?

Have you had all the maintenance performed per the manual including the valves checked and adjusted? The 3.8 engine has solid lifters. At 91k the valve lifters may need adjustment.

 

[Mark_888]

I have a 2009 3.8 Genesis sedan black 91k. I have been using supreme unleaded if I am saying it right for a year. I have read many comments and trying to inquire from dealers. Is regular unleaded purfered for the 3.8? My gas mileage is not great with supreme nor does it accelerate smoothly like when I first got it. I have only had it for 2 years purchased "used" love it. I just need to know is regular unleaded best for the 3.8 sedan?

Hyundai specifies regular grade fuel for the 3.8 V6. This information is in the Owner's Manual. If you don't have one, join MyHyundai on their website and download it.

I typically use 1/3 premium and 2/3 regular, especially in the summer. 100% premium may be too much octane, especially in winter.

 

[Madhornet 18]

Thank you

 

[427435]

Hyundai specifies regular grade fuel for the 3.8 V6. This information is in the Owner's Manual. If you don't have one, join MyHyundai on their website and download it.

I typically use 1/3 premium and 2/3 regular, especially in the summer. 100% premium may be too much octane, especially in winter.

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You can have too little, but too much hurts nothing.

 

[Mark_888]

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You can have too little, but too much hurts nothing.

Maybe, maybe not. I have heard anecdotal remarks on this forum from people who use 100% premium, and they say the car does not run well when it is really cold outside.

I am not saying it hurts the engine, but may not run as well in some situations.

 

[Nikgen]

Hyundai specifies regular grade fuel for the 3.8 V6. This information is in the Owner's Manual. If you don't have one, join MyHyundai on their website and download it.

I typically use 1/3 premium and 2/3 regular, especially in the summer. 100% premium may be too much octane, especially in winter.

Are you saying you mix at the pump as you fill? Sounds a little crazy?

 

[427435]

Maybe, maybe not. I have heard anecdotal remarks on this forum from people who use 100% premium, and they say the car does not run well when it is really cold outside.

I am not saying it hurts the engine, but may not run as well in some situations.

If that is true, the difference is with the brand of the gas or the storage of it at a station. The only thing too much octane can hurt is your pocket book.

 

[Mark_888]

If that is true, the difference is with the brand of the gas or the storage of it at a station. The only thing too much octane can hurt is your pocket book.

Keep in mind that I am talking about the V6, not the V8.

 

[Mark_888]

Are you saying you mix at the pump as you fill? Sounds a little crazy?

Yes, what they charge for mid-grade is a rip-off. It is cheaper to mix my own. Also, when I get gas at Costco, they don't have mid-grade.

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[Nikgen]

Yes, what they charge for mid-grade is a rip-off. It is cheaper to mix my own. Also, when I get gas at Costco, they don't have mid-grade.

Err...Ok...seems a little much - the pump attendant and the folks in line behind you must love you as doesn't that require 2 transactions?

 

[Mark_888]

Err...Ok...seems a little much - the pump attendant and the folks in line behind you must love you as doesn't that require 2 transactions?

Yes, two transactions. I use two different credit cards and pay at the pump (no attendant). It is extremely rare that anyone is behind me when I get gas. I only get gas about once a month these days.

 

[Nikgen]

Yes, two transactions. I use two different credit cards and pay at the pump (no attendant). It is extremely rare that anyone is behind me when I get gas. I only get gas about once a month these days.

Do you do some donuts around the parking lot to mix the tank afterwards to make sure you have a uniform mid grade?

 

[Mark_888]

Do you do some donuts around the parking lot to mix the tank afterwards to make sure you have a uniform mid grade?

I only do donuts at Krispy Kreme.

 

[427435]

Keep in mind that I am talking about the V6, not the V8.

The affect of too much octane (which is none) would be the same regardless of engine configuration.

 

[Mark_888]

The affect of too much octane (which is none) would be the same regardless of engine configuration.

There is a reason why refineries change the gasoline formula in the winter versus summer. In very cold weather, too much octane is not optimal unless the engine is running at very high speeds for a long time.

 

[Nikgen]

There is a reason why refineries change the gasoline formula in the winter versus summer. In very cold weather, too much octane is not optimal unless the engine is running at very high speeds for a long time.

That's completely wrong - the octane level is not changed seasonally - what they actually do is manipulate the blend to adjust the Reid Vapor Pressure of the fuel. This is necessary to allow for efficient operation of the engine in summer versus winter temperatures as well as for pollution concerns of excessive fuel evaporation to the atmosphere in summer high temps. Here's a good explanation from AAA:

"The difference between summer- and winter-blend gasoline involves the Reid Vapor Pressure (RVP) of the fuel. RVP is a measure of how easily the fuel evaporates at a given temperature. The more volatile a gasoline (higher RVP), the easier it evaporates.

Winter-blend fuel has a higher RVP because the fuel must be able to evaporate at low temperatures for the engine to operate properly, especially when the engine is cold. If the RVP is too low on a frigid day, the vehicle will be hard to start and once started, will run rough.

Summer-blend gasoline has a lower RVP to prevent excessive evaporation when outside temperatures rise. Reducing the volatility of summer gas decreases emissions that can contribute to unhealthy ozone and smog levels. A lower RVP also helps prevent drivability problems such as vapor lock on hot days, especially in older vehicles."

http://newsroom.aaa.com/2013/06/what-is-the-difference-between-summer-and-winter-blend-gasoline/

Here's some good info on gasoline blend details, for those so inclined:

http://www.theoildrum.com/story/2006/9/13/234043/431

 

[Mark_888]

That's completely wrong - the octane level is not changed seasonally

I didn't say they changed the octane level. I just said "formula." The point is that the same gas does not always work in all different weather conditions.

 

[Nikgen]

I didn't say they changed the octane level. I just said "formula." The point is that the same gas does not always work in all different weather conditions.

Sorry, but you implied exactly that!

You said:

"There is a reason why refineries change the gasoline formula in the winter versus summer. In very cold weather, too much octane is not optimal unless the engine is running at very high speeds for a long time."

So your statement implied that the refineries change their formula because too much octane is not good in cold weather. That is just plain incorrect - regardless of how you want to spin what you actually wrote.

The "formula" change for cold weather does not lower octane levels (in fact, it might actually result in slightly higher octane levels in winter fuel depending on what they blend).

 

[Mark_888]

Sorry, but you implied exactly that!

You said:

"There is a reason why refineries change the gasoline formula in the winter versus summer. In very cold weather, too much octane is not optimal unless the engine is running at very high speeds for a long time."

So your statement implied that the refineries change their formula because too much octane is not good in cold weather. That is just plain incorrect - regardless of how you want to spin what you actually wrote.

The "formula" change for cold weather does not lower octane levels (in fact, it might actually result in slightly higher octane levels in winter fuel depending on what they blend).

No, I did not imply that. However, I did say that changing the octane can have similar effects as the changes you describe above for the changes that are made which do not change the octane rating. I stand by that claim.