87 or 91 octane gas

[Nagloc68]

I searched the forum and couldn’t find a related thread. If there is one, feel free to point me to it.

Original Owner of a 2013 Yukon xl Denali with 191k. Original car, well maintained but stock, original tune so maintains the V8/V4 feature. We have used 87 octane its whole life. Have been reading a bit and have interpreted some comments suggest 91 octane is preferred. But it has always been about $1 more a gallon which is why we used 87. Most of its gas has been purchased at our local Costco which is top tier. 91 is currently $5.23 at Costco!

Engine drives strong and hasn’t caused any concerns. Much of my miles are highway miles. My question is at 191k miles is there any reason to change the octane of gas I use?
Thanks

 

[donjetman]

If you want to extend your range/mpg? run premium. In our Denali (mostly hwy) premium pays for itself.
GM recommends premium with our 07 6.2L L92.
I experimented w/87 and 89 unleaded and gas mileage suffered and I got an occasional "Knock Detected" on the digital info center, not good.
Your vehicle may have lower compression and be tuned from GM for regular? In that case premium would have no effect

 

[Joseph Garcia]

I searched the forum and couldn’t find a related thread. If there is one, feel free to point me to it.

Original Owner of a 2013 Yukon xl Denali with 191k. Original car, well maintained but stock, original tune so maintains the V8/V4 feature. We have used 87 octane its whole life. Have been reading a bit and have interpreted some comments suggest 91 octane is preferred. But it has always been about $1 more a gallon which is why we used 87. Most of its gas has been purchased at our local Costco which is top tier. 91 is currently $5.23 at Costco!

Engine drives strong and hasn’t caused any concerns. Much of my miles are highway miles. My question is at 191k miles is there any reason to change the octane of gas I use?
Thanks

Many threads and opinions on this topic, and it has been discussed ad nauseum on this Forum. I did a quick search, and surprisingly, I found very little on this topic, just as you experienced. We really need a better search engine on this Forum.

Bottom line, some use 87 octane, but most use 91 octane, as recommended by GM. If you are at 191k miles using 87 octane without any issues or knocking, then I'd say keep on using it.

 

[Doubeleive]

I searched the forum and couldn’t find a related thread. If there is one, feel free to point me to it.

Original Owner of a 2013 Yukon xl Denali with 191k. Original car, well maintained but stock, original tune so maintains the V8/V4 feature. We have used 87 octane its whole life. Have been reading a bit and have interpreted some comments suggest 91 octane is preferred. But it has always been about $1 more a gallon which is why we used 87. Most of its gas has been purchased at our local Costco which is top tier. 91 is currently $5.23 at Costco!

Engine drives strong and hasn’t caused any concerns. Much of my miles are highway miles. My question is at 191k miles is there any reason to change the octane of gas I use?
Thanks

your good, no reason to start paying more now.
if you want a tiny bit more giddy up use e85 if you have it available, you might not feel the difference though

 

[Foggy]

It's a high compression engine.. So it requires 91 octane. Just like
it says in manual.
IF you run lower octane, it will knock/detonate... Then Ecm will adjust to
the low octane spark table (of course after some knock-bad- is detected)
It will stay in that low octane table and your gas mileage will suffer.
So it's up to you to justify what it wants - 91 octane
You can risk knock/pre ignition/detonation and worse mpg OR
just put in what it's designed to run

 

[mikez71]

I thought that was one of the benefits of the 6.0 over the 6.2, to ability to reliably run regular gas?
Though being at 191k on the 6.2, that sounds pretty reliable...

 

[the 18th letter]

I searched the forum and couldn’t find a related thread. If there is one, feel free to point me to it.

Original Owner of a 2013 Yukon xl Denali with 191k. Original car, well maintained but stock, original tune so maintains the V8/V4 feature. We have used 87 octane its whole life. Have been reading a bit and have interpreted some comments suggest 91 octane is preferred. But it has always been about $1 more a gallon which is why we used 87. Most of its gas has been purchased at our local Costco which is top tier. 91 is currently $5.23 at Costco!

Engine drives strong and hasn’t caused any concerns. Much of my miles are highway miles. My question is at 191k miles is there any reason to change the octane of gas I use?
Thanks

At 191k with AFM enabled I can’t think of one reasonable argument to change octane at this point. Not one…this is assuming you haven’t rebuilt the motor at any point already since you said ‘original car’.

 

[Foggy]

I thought that was one of the benefits of the 6.0 over the 6.2, to ability to reliably run regular gas?
Though being at 191k on the 6.2, that sounds pretty reliable...

Yup . The 6.0 in the 2500hd has the cast iron block and lower compression
Also NO DOD and a little diff cam profile than the 6.2
So it doesn't need the higher octane

 

[Bill Barnes]

I read all of the replies on this thread, and agree with most of them. Here in Virginia, we have a convenience chain called Sheetz, and it offers an 88 octane E15 gas that is always about 40 to 50 cents a gallon less than the 87 octane regular E10. The pump handle and selection button are color coded in blue. My 2005 Yukon XL 5.3 FLEX Fuel 4X4 likes it just fine. I have 300K miles on the vehicle, and I've been using the 88 octane E15 for 100K with no problems, and maybe a tiny bit better mileage, maybe 5%.

 

[donjetman]

Ethanol has less energy (BTUs) per gallon than gasoline so mileage/range suffers, but it cheaper.

I've run mixtures of as much as 30% ethanol and no issue(s).

 

[LsHart]

Run what it calls for.

 

[Nagloc68]

Thanks guys. I appreciate the comments and input. No engine rebuild (knock on wood) !

 

[Marky Dissod]

It's a high compression engine.

L92/L9H/L94 are NOT high (static) compression engines - L76s (not truck L76, car L76s) and L77s also have 10.4:1 static compression, and run 87 just fine.
NOT a recommendation, but you can GET AWAY with it - that's what the low octane table is for. You SHOULD use 91. I don't talk to adults like they're kids,
all y'all apparently forgot the original '07 L92's power rating of 380 horses on 87 octane:

I'll NEVER recommend 87 in an L92/L9H/L94, neither does GM, but GM was never against 87 either.
91 octane is worth at least 20 horsepower, according to GM; see pic above.
GM OE tuneS are the major variable here - I've not yet compared '07 L92 calibrations to later ones. Has anyone?

 

[LSCALADE]

2013 is a flex fuel L94 so mix 87 with E84 and you get something around 93-94 octane.

If you have a way to log knock retard events, you will see that the engine is constantly pulling 4-6deg of timing at every event. You may not feel it or hear it but its there and its wasting fuel and reducing power. When I mix E85 in the mix so 2gal 87 to 1 gal E85 knock disappears entirely; that tell you something. So a mix of E85 or 91/93 is the sweet spot if you want this thing to last.

These engines are high compression and with mileage they do accumulate carbon deposits on the piston tops, which with heat start to glow and further cause detonation events. I have a Cammed 6.2 that absolutely hates seeing anything less than 93 in the tank but its tuned and non flex capable so it has to run 93. Fun truck but I hate its gas mileage.