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Premium Fuel in 5.3L. More power or placebo effect?


raym0016

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Yesterday I filled up my tank for the first time with top tier premium. The first tank was from the dealer and I put 300 miles on, was below 1/4 tank and decided to fill it up. I put 18 gallons of 91 octane (top octane in my area) and it just seems to have a tiny bit more get up and go. I am not sure if this is my mind playing tricks or if this is really possible. Considering this is really 18 gallons of 91 and 6 gallons of 87, I am suspecting that my mind is playing tricks on me.

 

For those who have done more extensive "testing", does anyone else have a similar experience with a 5.3L? Is there a difference in "pep" between regular and premium? How about MPG any difference there?

Edited by raym0016
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On non-DI engines, there is no increased power/pep from higher octane fuel. The higher octane reduces preignition and associated "ping." For engines that are setup to produce high horsepower from combustion ratios, etc., the higher octane would be required to control the fuel ignition. No idea if the 5.3 having DI makes a difference but I doubt it does.

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Octane number does not directly mean more power. The octane number only represents the fuels resistance to detonation. Higher octane is need for vehicles with higher compression ratios to help avoid knocking or pre detonation.

 

In fact the opposite is true, higher octane fuels produce less energy per volume than lower octane fuels.

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I ran a test of this when I had my 2014 with the 5.3L. I consistently averaged 17 - 18 mpg over many tanks with my normal daily driving habits. I switched to 93 octane for several tanks and averaged the exact same mileage over those tanks. I know that mileage doesn't necessarily equate to "power", but it's a reference point.

 

Like agentf said, octane is just the ability of the gas to resist early detonation.

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Most likely a placebo effect. But you will probably notice slightly better gas mileage (emphasis on slightly) with the higher octane and a smoother running engine. The DI engines like the higher octane because they have such high compression.

 

When i first got my truck, I would run 87 octane. I noticed the truck would stumble and sometimes rpms would drop below 500 at idle. Switched to 89 octane and it was fine. So since then I would run 89 octane pretty much exclusively.

 

But ever since getting a Blackbear tune, I have been using 93 octane.

 

I will also note, that even stock motors, Blackbear Performance recommends at minimum 89 octane for the 5.3. I would assume the same for the 4.3. And 6.2 motors should be using 91+.

Edited by fondupot
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Thanks for the feedback. Perhaps it is placebo, that is what I thought. Maybe it has something to do with the quality of gas? I can only assume that the dealership put 87 gas that wasn't necessarily "top tier" like the premium I got, may be that is what I am feeling. Maybe it is more a matter of things breaking in since I now only have 340 miles on the truck.

Edited by raym0016
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I unfortunately did not get a truck that was E85 compatible. I am not sure why but they are very few and far between on the lots. There were more earlier in the year but none of the newer 2015 that the dealers took delivery on were equipped with E85 since June or July. I am not sure why that is the case. I heard that GM was phasing it out but that may have been unsubstantiated rumor. I find it odd, being in MN where E85 is actually fairly common.

 

 

If you want an increase in power from the pumps try some E85. I believe that its a 25HP increase. with a 25% decrease in fuel economy.

 

E85 is an option If your vehicle is compatible.

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I have tested through quite a few tanks of each 87, 89, and 91+ and I can say that 89 seems to be a sweet spot for my truck. I could not see a difference in my MPG calculations, or my butt-dyno, between 89 and premium. However, when I went from 87 to 89, I see smoother idle, smoother acceleration, and 1-2 mpg better fuel economy. It more than makes up for the extra $2 per fill up.

 

I do not have a tune, but have spent significant time reading everything I can about our engines. Black Bear Performance seems to be one of the best when it comes to tuning our trucks. Therefore, I think I would trust them and their advice on this subject. They have the following info in the FAQ section of their website.

 

  • 2007+ 5.3L engines. At 10:1 compression, this engine (all variants) cannot run efficiently on 87 octane. Power output and mileage will be noticeably better in 95%+ vehicles simply by switching from 87 to 89 octane. 91+ preferred.
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As posted above, I would get some hesitation or stumbling with 87. When I run 92, I rarely see this. So, I use 91/92 all the time now. With double coupon tuesdays, it's the same price as regular anyway. ;).

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An increase in millage is what I see since the 91 at Costco has no ethanol in it in Canada.

 

I usually run it in the Winter more since the truck hates winter gas it gets me the most millage I can get since the truck drops down to 15MPG on the winter gas.

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I have a little over 1000 miles on my truck now and have gone through a couple of tanks of 87.

The truck feels like it accelerates and shifts smoother now than when I first got so either it has broken in, it has 'learned' my driving habits, or I have adjusted to its idiosyncrasies.

In any case I am loving driving it and I'm getting better mpg than my old f150 so I am very pleased.

It is a 5.3 with the 3.42 rear end, 2wd.

Edited by crewl1
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... Maybe it has something to do with the quality of gas? I can only assume that the dealership put 87 gas that wasn't necessarily "top tier" like the premium I got, may be that is what I am feeling. Maybe it is more a matter of things breaking in since I now only have 340 miles on the truck.

 

I think this is the key here. It's not necessarily the grade of fuel, but rather the quality. I filled up with premium 91 at a local grocery store pump, and my truck ran like crap for the entire tank. Once empty, I filled up with 89 from the QT down the street. Instant difference. No so much power, but smoother starting and running when cold, less hesitation on acceleration, and no stuttering. If this modern ethanol laced fuel sits too long or isn't transported properly, it can absorb a lot of moisture. This literally dilutes the fuel and makes it burn terrible.

 

I had a conversation with a mechanic at a local European motorcycle shop here in Plano. They deal in BMW, Ducati, Triumph, and a few other boutique brands. He said they did an extensive search locally for the best gas to put in these temperamental bikes, where the 'butt dyno" is much more accurate. He swears by QT fuel. He said they found it was always the "freshest" and the bikes never have a problem with it.

 

That's good enough for me to stick with QT when I can. And stick with the 87 octane.

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