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Wow...89 Octane In 5.3l

newdeal

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newdeal Enthusiast

newdeal

Posted
Posted

So I was at the station today and they had the same price on the 89 octane as the 87 octane so I decided to try the 89 octane just for fun even though I know everyone says it will make no differance. Well the whole way home I was driving trying to see if there was a tail wind because it was doing far better on gas than normal (I just got it so I drive with the fuel mileage display and watch it as I go). I am in Canada so its L/100km but I was doing 11-12L/100km on the highway with the cruise locked and on that same stretch I am normally getting 14L/100km. Seems like 89 so far has increased my economy by about 20% and I can also tell it will hold V4 at much higher speeds than before. With the 87 basically it hit V4 if I had a steady foot below 60kmph and only if it was downhill on the highway, now I can drive 80kmph and get it to hold in V4. This was consistant and the drive from the gas station to my house is around 45km (I drive to the states to fill up because gas is about $1.20 a gallon cheaper there)

502ci Enthusiast

502ci

Posted
Posted

If your truck is completely stock without a tune the higher octane (it burns slower)should actually hurt your performance and mileage if anything...I won't be the only one to say this, get ready for alot of skeptics to comment.

newdeal Enthusiast

newdeal

Posted
  • Author
Posted
If your truck is completely stock without a tune the higher octane (it burns slower)should actually hurt your performance and mileage if anything...I won't be the only one to say this, get ready for alot of skeptics to comment.

 

yes it is totally stock. I will continue tracking it but so far it seems to be excellent. Now I had no intention for it to do anything but I figured if it was the same cost why the heck not

Matt_ Senior Enthusiast

Matt_

Posted
Posted

even if it was tuned... it'd take a few hundred miles to actually make a difference.

 

just saying.

 

keep tracking it. i bet your fuel mileage goes right back to what you're used to seeing.

KMGZ400 Senior Enthusiast

KMGZ400

Posted
Posted

im my suburban one time i was completley empty, filled it up with 93, (i always run 87) and after 6 days, i was getting 14mpgs instead of 16mpgs and that was not according to the DIC

newdeal Enthusiast

newdeal

Posted
  • Author
Posted

why would it take a couple hundred miles to see a differance? If I drive the same stretch of road and am watching the instantaneous mileage on the DIC then shouldn't it be instant?

Matt_ Senior Enthusiast

Matt_

Posted
Posted

it takes time for the computer to adjust for optimizing.

 

keep tracking it over a longer period of time and see what happens. A 20% increase in gas mileage IMMEDIATELY after filling up with a new octane is almost unheard of, even for a tuned truck.

 

Not saying it couldn't happen. But i wouldn't jump to any conclusions based on that one trip :rolleyes:

redvett Senior Enthusiast

redvett

Posted
Posted

Also the fuel you had left in the tank was 87 so you just diluted the 89 down some and like "MATT" said the PCM need at the least 100 miles to adjust to the different octane.

kdixer Enthusiast

kdixer

Posted
Posted

When black bear tuned my truck he suggested I run atleast 89 due to the knock retard that was showing up in the initial logs I sent in. I had also noticed on a diablo handheld tuner I used to have that the factory tune had more spark advance than diablo's tunes. I cannot explain this with any certainty. But I can say that sometimes a factory tuned vehicle will most certainly run better with a higher octane fuel.

 

I do not know what the specs are on the compression ratio of the 5.3. But my 09 Silverado has the non flex fuel Aluminum block 5.3. When I look at my ECM file using efilive, the compression ratio is listed as 10.5 to 1. But there is a discrepancy on the model. The vin read shows it being a k2 - 2500 (3/4 ton) but it is a 1500. So i do not know if something was screwball with my tuning from the factory or if my truck is some high compression version of the 5.3, I just do not know. I know Gm has made high output versions of certain engines and for whatever reason, there are different power ratings for the 5.3 depending on what vehicle it is used in. So I just have not made sense of this yet.

SouthCo Senior Enthusiast

SouthCo

Posted
Posted
If your truck is completely stock without a tune the higher octane (it burns slower)should actually hurt your performance and mileage if anything...I won't be the only one to say this, get ready for alot of skeptics to comment.

 

 

Higher octane fuel doesn't burn slower, it has a higher flash point. There is a difference. It will not hurt performance. If the ecm is retarding timing due to a knock condition, it will help performance to run a higher octane. If the ecm is never retarding timing, it will not help performance, but it won't hurt it either. In colder temps, it's more likely to help(I think).

jro909 Senior Enthusiast

jro909

Posted
Posted

only way i can think of that would lead to more mpg without an octane tune would be the lack of ethanol in the fuel :rolleyes:

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted
only way i can think of that would lead to more mpg without an octane tune would be the lack of ethanol in the fuel :rolleyes:

 

In Ontario it is common to find that reg has ethanol and the other grades do not. I would tend to think it was more likely a tailwind in this case. I have found that these trucks really like a good tail wind for mileage.

BTW, in my case, using the non-ethanol fuel makes enough of a difference in mileage to account for the higher cost of the mid-range fuel.

ybsane Enthusiast

ybsane

Posted
Posted
When black bear tuned my truck he suggested I run atleast 89 due to the knock retard that was showing up in the initial logs I sent in. I had also noticed on a diablo handheld tuner I used to have that the factory tune had more spark advance than diablo's tunes. I cannot explain this with any certainty. But I can say that sometimes a factory tuned vehicle will most certainly run better with a higher octane fuel.

 

I do not know what the specs are on the compression ratio of the 5.3. But my 09 Silverado has the non flex fuel Aluminum block 5.3. When I look at my ECM file using efilive, the compression ratio is listed as 10.5 to 1. But there is a discrepancy on the model. The vin read shows it being a k2 - 2500 (3/4 ton) but it is a 1500. So i do not know if something was screwball with my tuning from the factory or if my truck is some high compression version of the 5.3, I just do not know. I know Gm has made high output versions of certain engines and for whatever reason, there are different power ratings for the 5.3 depending on what vehicle it is used in. So I just have not made sense of this yet.

 

"When black bear tuned my truck he suggested I run atleast 89 due to the knock retard that was showing up in the initial logs I sent in. I had also noticed on a diablo handheld tuner I used to have that the factory tune had more spark advance than diablo's tunes. I cannot explain this with any certainty. But I can say that sometimes a factory tuned vehicle will most certainly run better with a higher octane fuel."

 

That is true for me also..! My tuner noticed I had a knock in my vehicle and suggested I run 89 Octane. After doing so for about a month i went back to him and he checked the timing while we I was driving it and said I should be happy there.

 

Also why do people not read their owners manual, they love to quote from it on this forum and plainly states to use 87 Octane as the lowest requirement, my dealer has said the same thing to me especially for people who tow.

 

Rob

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