Fuel grade

[Marky Dissod]

When you say 'pull timing', do you mean the knock counts are increasing every time spark advance is reduced?
That's my understanding of knock retard.
IF GM wrote the High Octane Table over what 87 could possibly achieve without knocking, then I get why I was wrong.

You can not run E85 in a non flex fuel vehicle and expect good performance.
Yes it will run but it will do so at reduced performance.

Without an in-person tune this is blatantly obvious.
If I misrepresented this also, then also my bad. Non- Flex Fuel vehicles should not run E85, unless tuned to do so.

 

[THarber]

When you say 'pull timing', do you mean the knock counts are increasing every time spark advance is reduced?
That's my understanding of knock retard.
IF GM wrote the High Octane Table over what 87 could possibly achieve without knocking, then I get why I was wrong.
Without an in-person tune this is blatantly obvious.
If I misrepresented this also, then also my bad. Non- Flex Fuel vehicles should not run E85, unless tuned to do so.

No everytime the knock sensor records a knock, it will cause the ecm to retard the timing, that's pulling timing. It will continue to do so until the knock is gone. WHen you pull 15 degrees or more of advance out of these trucks, you might as well tie a boat anchor to the back of them. These engines have 11.5 to 1 compression yet due to head design they run extremely well even on 91 octane. They are tuned for this from the factory and when the fuel requierement is not met, all that can do is retard the timing and reduce gpm at the injector, neither of which is an ideal situation. Repeated knock can bust a piston or the top ring land or ring.

 

[morig]

For a highway based roadtrip is there an advantage/disadvantage of running 87 octane versus 91? Same question for city driving?

 

[Scott in AZ]

At 14,000 miles per year, divided by 14 miles per gallon, our Tahoe or Yukon uses about a thousand gallons of gas per year. So premium 91 octane gas costs about $500 bucks a year more than 87 Octane, assuming $0.50 more per gallon. And this completely neglects that we’re actually getting slightly better fuel efficiency with better grade gas, so the difference is probably less than $500.

For some people $500 is a big deal. For most of of us, probably not.

Me, I’ve run 89 Octane mid-grade in my 2001 5.3L for the last 22 years, but after thinking thru this I might try a few tanks of 91-premium and see if it makes any difference in drive-ability or my long term fuel economy average 14.9 MPG.

 

[Vladimir2306]

In Russia, we have a slightly different method for estimating the octane number of gasoline. So we have the 92nd, it's like the 87th in the USA. There's a 95th that's about the 89th in the US, and a 98th is like a 91st in the US... We also have 100th gasoline .. It's about like the 95th in the United States .. It is used for powerful motors. So. I drive our 95th. It's like your 89th.. And no problem. There are acquaintances who drive the 92m. It's like the 87th in the USA .. There is also no mileage even with a mileage of 100-150 thousand km. It's just that the car drives a little worse and the consumption is a little more

 

[WalleyeMikeIII]

FWIW, I ran Costco 92 Top Toer for the first 12-13k miles. Found a Sinclair in my town that had 93 Top Tier for $0.05 more per gal than the Costco, but using the DINOPAY app takes $0.10 per gallon off. So that’s what I run now. Notice slightly less carbon on the tailpipes using the Sinclair. The 6.2 loves this fuel…smooth as butter.

 

[BG1988]

Recommended ... Not QUITE the same as required ...

Not nearly as well on 87 as it would on 91 octane, in terms of fuel economy, throttle response, performance measured against a stopwatch, and overall engine longevity.
The harder you drive, the better your engine will operate, the further the engine will go, and the longer your engine will last, with 91 octane.
The lazier easier you drive, the more you can get away with 87 octane - even then, 91 octane is ALWAYS better.

In the case of 6.2L V8s, using 87 for anything other than minimally demanding driving - one driver, no riders, unladen, unburdened, unhurried - may result in drivability symptoms that would not normally occur using 91 octane.

Whether or not you suffer symptoms using 87 that can be avoided with 91 depends as much on how it's being driven, as how well it's been maintained.

Just 'cause you can, doesn't mean you ever should.
I would NEVER tow / haul / drive 'hard' without using 91 octane in any 6.2L.

(My educated guess is that using 87 octane 'costs' anywhere 15 - 25 ft-lb of torque, regardless of RpM.)

last night I was racing a guy in his DuraMax he got beat by a hybrid LOL I use 91 octane i'm guessing he didn't know about my Intsta torque.. didn't even have to put it in M4

he tried so hard though... bet he redlined it for sure(sounded like it..)... I barely made it to 2700rpm LOL he was barely able to keep up with me..


you're not rolling coal on me bro He tried using his bar light to try to blind me and also failed i'm guessing he forgot i got a hatchback? all i did was point my side mirror back into his face... he ended up shutting it off what a sore loser

 

[Eusibius2]

last night I was racing a guy in his DuraMax he got beat by a hybrid

@BG1988 What truck or car were you driving?

 

[BG1988]

2008 tahoe HYBRID