Does a 2024 Z51 with 6.2 require premium fuel?

Marky Dissod said:

If driven hard, if the engine is working or playing hard with 87, the pcm / ecm IS responding to detected knock AFTER IT HAPPENS by pulling timing back, and possibly adding (wasting?) fuel to cool the cylinders.
The pcm / ecm NEVER learns this. It never predicts or avoids knock.

Click to expand...

Is this not EXACTLY what the burst knock retard table is for? Pulling timing for expected knock...

It obviously needs to see some knock to retard the timing for a lower octane fuel since I don't believe it has any other way to know the fuel is going to detonate more easily than for it to just go ahead and let it do that but burst knock table has been around awhile. Never say never... or something like that.

gtrslngrchris said:

Is this not EXACTLY what the burst knock retard table is for? Pulling timing for expected knock?

Click to expand...

It doesn't retard timing, so much as it slows timing changes to give fueling a better chance of not going lean.
Lean however does not automatically mean knock, but it usually means more NOx.
In practice I've found that burst knock usually just dulls engine throttle response.

gtrslngrchris said:

It obviously needs to see some knock to retard the timing for a lower octane fuel, since I don't believe it has any other way to know the fuel is going to detonate more easily than for it to just go ahead and let it do that ...

Click to expand...

The ecm never KNOWS what octane fuel is in use, it just interpolates between the High & Low Octane spark tables.
Any sufficient TPS% increase per unit of time, and it goes back to the LOW octane table AND adds a wee lil bit o' burst knock just before it enriches a bit.

Direct injection engines can be better at preventing knock than multiport injection - operative words being 'can be'.
If I can afford a brand new vehicle, but I can't afford 91 or 93 octane, then I should buy two used vehicles and tune their ecms for 87 octane.

All of you talking about fuel prices in the $2-$3 range are killing me, I was excited to see 91 at $4.45/gal after seeing 87 at $5+/gal for so long!

swathdiver said:

Did you measure this with a scan tool of some kind or your ears?

Click to expand...

Both methods were used during different times of the day, and under different driving, idling, and temperature conditions. You can also use a decibel tool too.

ProfeZZor X said:

Both methods were used during different times of the day, and under different driving, idling, and temperature conditions. You can also use a decibel tool too.

Click to expand...

And what did you see on the scan tool?

NorthGeorgia said:

I am somewhat hesitant to contribute here for fear of maybe not knowing what I am really talking about. I just purchased new a 2024 Tahoe 'High Country'. My ignorance is going to say I'm not sure what 'gas' engine I have but I will assume it's not the 6.2 being debated here? But I am going to say that I have been pleasantly surprised with the mpg's I got on a 450mile round trip I just took. On the way 'there' I averaged 24+mpg. On the way back I averaged 23+mpg. Admittedly I was only going 66mph on the highway. This is what the onboard 'computer' indicated. I think the window sticker indicated that this vehicle listed the mpg's at 14 to 18? So I am greatly happy and surprised or........the computer is not telling me the truth????

Click to expand...

You can always check your mileage with traditional math calculations. I have a Fuelly app that I log all gas purchases for my last 3 vehicles. Sometimes I’m better than the computer indicates, sometimes I’m not.

...

swathdiver said:

And what did you see on the scan tool?

Click to expand...

yo' momma..... Just kidding, my friend. Not sure what kind of answer I'm supposed to give you on that one, seeing as some electronic tools are meant to visualize or audibly provide readouts.

ProfeZZor X said:

yo' momma..... Just kidding, my friend. Not sure what kind of answer I'm supposed to give you on that one, seeing as some electronic tools are meant to visualize or audibly provide readouts.

Click to expand...

Did you see any knock with the scan tool while driving with low octane fuel at WOT? If so, how much? That's what I mean.

You can set up some scan tools to show you which cylinders detected knock and pulled timing.

swathdiver said:

Did you see any knock with the scan tool while driving with low octane fuel at WOT? If so, how much? That's what I mean.

You can set up some scan tools to show you which cylinders detected knock and pulled timing.

Click to expand...

To that, I would say no. There was no significant difference in noise, that would cause for alarm. Is there noise coming from the engine bay, yes, but as you'd expect for a 22' vehicle with close to 60k miles on it, that's the kind of wear and tear you'd expect to happen.

Hope that answers your question.