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Lower Octane Or Higher?

punmax

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punmax Senior Enthusiast

punmax

Posted
Posted

Hey everyone, I've been putting 87 octane in my Silverado (6.0). If I switch to 91, will it make the engine perform better? Does it help with smooth idiling? What are the effects of it, thanks.

Scotty-B Enthusiast

Scotty-B

Posted
Posted

No. It could cause it to start pinging or deteriorate how it runs right now. The engine has been tuned for the 87, If you want to run different octane from what the manufacturer says should be in it, get a tune that allows for proper timing advances and whatever else is needed to optimize the performance for it.

svensk Senior Enthusiast

svensk

Posted
Posted
No. It could cause it to start pinging or deteriorate how it runs right now. The engine has been tuned for the 87, If you want to run different octane from what the manufacturer says should be in it, get a tune that allows for proper timing advances and whatever else is needed to optimize the performance for it.

Your truck has a vortec L76 which is a higher compression 6.0L. You might see gains by running a few tanks of 91. You won't ruin the engine that's BS.

wlvrn1215 Senior Enthusiast

wlvrn1215

Posted
Posted

I highly doubt pinging would occur by putting higher octane fuel in.... it doesnt work that way :sigh: the computer adjusts for timing automatically

pm26 Senior Enthusiast

pm26

Posted
Posted
I highly doubt pinging would occur by putting higher octane fuel in.... it doesnt work that way :sigh: the computer adjusts for timing automatically

 

And even in an old 70's truck, higher octane helps stop the pinging, not cause it.

punmax Senior Enthusiast

punmax

Posted
  • Author
Posted

In the GM manual, does it say use premium fuel? I would check myself, but it's raining hard outside and I don't want to get wet :sigh:.

Rocco715 Enthusiast

Rocco715

Posted
Posted

the 6.0's don't require premium but the 6.2's do. You might notice a slight increase but it won't be much considering your truck is new. The computer will automatically adjust for the higher octane but I have heard rumors where if the fuel is too high in octane not all of it will be burned and the deposits will be left in the engine but don't hold me to that. I split the difference and only use mobil 89 and when I crank up my Edge Evolution Mobil 93.

the hammer Enthusiast

the hammer

Posted
Posted

Octane is the rating that shows how well that grade (octane level) of gasoline controls the burn. Higher octane allows better control of the burn and thus more advanced timing is allowed, giving more power and a better performing engine. Octane is a pre-detonation control chemical. So, the higher the octane, the less likely of misfire/predetonation due to hot spots in the engine. The higher your octane level, the better the computer can control the spark timing and the correct desired ignition point of the fuel.

 

Higher octane all the way! I never use anything less than 93, even 89 made my truck run worse. I would switch to the higher grade you will be much happier.

HawkScot Enthusiast

HawkScot

Posted
Posted

The manual for the 08 Denali Yukon XL states premium fuel is RECOMMENDED, not required. It runs fine on regular, just doesn't have as much power and it does get lower MPG on fuel economy.

C & A s Dad Senior Enthusiast

C & A s Dad

Posted
Posted

Punmax, you have received some good info here except for the post that has already been identified as :lol:

 

I have been running 93 oct for a couple of years and according to my Interceptor Scan gauge, I have no (O) timing retard even on the hottest of days pulling my camper. One time when I was monitoring it, I saw a few second blip where it pulled a little timing ( 3 degrees if I remember correctly).

 

Your engine certainly has high enough compression to take advantage of some additional octane. It may not be a monumental change but I do get slightly better MPG with the 93 and my truck certainly pulls my camper better on 93. I cannot say I can see a difference in every day driving.

 

Modern high comp engines are able to run on lower octane because the computer controls detonation by reducing timing. It is sent a signal from the knock sensor/sensors and it pulls timing in a nanosecond. It slowly increases timing until the sensor hears the ping again and it pulls the timing back to stop it. The cycle happens over and over. With higher octane fuel, the ping does not come as often or possibly not at all so your system allows max timing meaning max power.

 

The posts in the past concerned about premium fuel leaving more deposits have never been explained. Someone has made this comment but cannot back it up.

 

One other thing because it will likely come up. Your Owner's Manual (at least mine) indicates a MINIMUM octane to run, in my case this is 87. It never indicates a max or offers any type of warning about running a higher octane. Also, I do not feel companies such as Chevron, Shell, BP etc could get away with advertising cleaner running engines by using their premium fuel if it were actually harmful to your engine.

 

Some people more knowledgable them me also say that you will need to run 2 to 3 tanks for the system to take full advantage of the higher oct.

 

Sorry for the long response.

omegafiler Senior Enthusiast

omegafiler

Posted
Posted

Exactly, same here. I've always noticed better performance when it was stock going from 87 to 93 octane. It's even more noticable with the larger engines, such as the 6.0's. My YD says minimum is 87 octane as well. It's doesn't actually recommend an octane. So that's just one of things you can experiment for yourself. It certainly won't hurt anything.

 

Now the TBSS does say recommended is premium. Obviously it can take 87 octane and will reduce power... but why would you buy a vehicle with such a powerful engine and not run it to it's full potential? If mileage & gas price is a big concern, I'd just suggest avoiding the more powerful engines to begin with. :lol:

hutcher1 Enthusiast

hutcher1

Posted
Posted

For what it's worth my 08 Silverado with a 5.3 went from 13.5-13.8 MPG to 15.3 - 15.5 on city driving when I switched from standard 87 to BP 91. Engine seems to run smoother to me as well.

ajcain79 Enthusiast

ajcain79

Posted
Posted

My owner's manual recommends a MINIMUM of 87 octane. Meaning 89, 91, and 93 are ok as well. Over christmas my family an I drove to orlando, FL. It was almost 3,000 miles roundtrip. On the way there I ran 87 octane and on the way back I ran 89 octane. I didn't notice any difference in power. My fuel mileage, however, on the 87 was 15.5mpg and on the 89 it was 16.5. So with a 1mpg improvement I pretty much broke even on the extra cost of the 89 octane. Maybe it would have been even better with the 91 or 93, but I never experimented with that. Maybe on the next road trip I will.

iminaquagmire Enthusiast

iminaquagmire

Posted
Posted

I've experimented a few times with premium in my truck and it does have more power. Fuel economy I can't say as I'm still on the first quarter of the first tank in a while. I'll have to wait and see in a few more tanks once the computer relearns and I stop WOT driving for my upcoming tune's data logging.

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