Good reason to run a 6.2 on premium fuel

[Snowbound]

Wouldn't mind seeing documentation on that. All of my information states that the L92s are 10.5:1.

Yeah, your documentation is correct. I just said 10:1 but technically it’s 10.5:1. Splitting hairs.
I also said you can’t tune for 87 octane but I guess technically that’s false too. You can try to pull timing and could in essence run 87, but at a ratio above 10:1 it’s best to just use premium. That $0.60 national average premium increase is not worth the lack of power, higher emissions and lower fuel mileage IMHO.

 

[Stbentoak]

I used to have a vehicle that would throw a CEL on 87, fill it back up on 93 ...light goes out. While you CAN use it, it isn't desirable or good for the engine. Buyers know this before purchasing, why cheap out afterwards...?

 

[donjetman]

The first yr we owned our 07 Denali we ran 87 octane and got a DIC knock sensor warning once. Then we ran 89 octane for a while, then 91+ for a while. Long trip gas mileage was:
15.5 on 87
16.5 on 89
17.5 on 91+
Then Swathdiver made a post #30: https://www.tahoeyukonforum.com/threads/best-octane-fuel-for-fuel-eceonomy-5-3l-only.120104/page-3

about running a mix of E85 and unleaded. So for 6 mths we ran a 25% of E85 and 87. All went well. But its not practical for us because the closest E85 is 20 miles away and its not convenient on our long hwy trips. Currently I'm running 91+, but as fuel prices rise I'll probably switch back to 87 or 89.

 

[wsteele]

The first yr we owned our 07 Denali we ran 87 octane and got a DIC knock sensor warning once. Then we ran 89 octane for a while, then 91+ for a while. Long trip gas mileage was:
15.5 on 87
16.5 on 89
17.5 on 91+
Then Swathdiver made a post #30: https://www.tahoeyukonforum.com/threads/best-octane-fuel-for-fuel-eceonomy-5-3l-only.120104/page-3

about running a mix of E85 and unleaded. So for 6 mths we ran a 25% of E85 and 87. All went well. But its not practical for us because the closest E85 is 20 miles away and its not convenient on our long hwy trips. Currently I'm running 91+, but as fuel prices rise I'll probably switch back to 87 or 89.
View attachment 345999

Looking at your results of MPG between grades and using the normal markup in these parts for 91 (pretty consistently 10% premium over 87, not counting Shell's propensity to jack that "nitro" stuff way up), it would seem using 91 is a no brainer.

I will be doing some comparisons of 87, 91 and E85 from the perspective of knock retard and knock sensor activity with the various grades in my 5.3L LMG engine (9:9 CR). I think I will also start keeping track of the MPG results as well. I already suspect my results will likely mirror yours with the 6.2L Denali.

Like you, E85 is a pain to get here and the prices are not commensurate with the shortage of BTU's, so I will likely only buy it for my tests.

 

[a4edwin]

I’ve been jumping back and forth between 89 and 91

 

[a4edwin]

The first yr we owned our 07 Denali we ran 87 octane and got a DIC knock sensor warning once. Then we ran 89 octane for a while, then 91+ for a while. Long trip gas mileage was:
15.5 on 87
16.5 on 89
17.5 on 91+
Then Swathdiver made a post #30: https://www.tahoeyukonforum.com/threads/best-octane-fuel-for-fuel-eceonomy-5-3l-only.120104/page-3

about running a mix of E85 and unleaded. So for 6 mths we ran a 25% of E85 and 87. All went well. But its not practical for us because the closest E85 is 20 miles away and its not convenient on our long hwy trips. Currently I'm running 91+, but as fuel prices rise I'll probably switch back to

The first yr we owned our 07 Denali we ran 87 octane and got a DIC knock sensor warning once. Then we ran 89 octane for a while, then 91+ for a while. Long trip gas mileage was:
15.5 on 87
16.5 on 89
17.5 on 91+
Then Swathdiver made a post #30: https://www.tahoeyukonforum.com/threads/best-octane-fuel-for-fuel-eceonomy-5-3l-only.120104/page-3

about running a mix of E85 and unleaded. So for 6 mths we ran a 25% of E85 and 87. All went well. But its not practical for us because the closest E85 is 20 miles away and its not convenient on our long hwy trips. Currently I'm running 91+, but as fuel prices rise I'll probably switch back to 87 or 89.
View attachment 345999

I thought you couldn’t run e85 in 07 Denali.

 

[wsteele]

I thought you couldn’t run e85 in 07 Denali.

I think he was referring to @swathdiver's results, which I think is a rare 2009 6.2L Tahoe (I could be totally wrong about his rig).

 

[donjetman]

I think he was referring to @swathdiver's results, which I think is a rare 2009 6.2L Tahoe (I could be totally wrong about his rig).

07 Denali w/L92 & 170k miles now.
For six months everytime I filled up I pumped 4 gals of E85 in, then roughly 16 gals of 87 octane. No issues at all. All this driving was rural. Operating cost per mile is lower if you have a good E85 source nearby. We do not. Our source is 20 miles away

 

[donjetman]

I think he was referring to @swathdiver's results, which I think is a rare 2009 6.2L Tahoe (I could be totally wrong about his rig).

I also did this same experiment on my 07 Toyota FJ Cruiser w/214k miles. It has 10.5 to 1 compression engine too. I've owned this vehicle for 12 yrs and have always run 87 octane. Toyota "recommends" 91+ octane.

A while back its mpg dropped from 20+ mpg to 18-19. Running a 25% mixture of E85/87 restored its mpg to 20+. I've got it back on 87 octane these days.

 

[wsteele]

07 Denali w/L92 & 170k miles now.
For six months everytime I filled up I pumped 4 gals of E85 in, then roughly 16 gals of 87 octane. No issues at all. All this driving was rural. Operating cost per mile is lower if you have a good E85 source nearby. We no not. Our source is 20 miles away

Got it, sorry to introduce more confusion.

Yes E85 is a pain here as well. The guy who owns the one pump with it is a used car dealer whose lot is across the street (Fairly Reliable Bob). he prices the E85 at the same exact price as the lowest 87 E10 (typically Costco), which makes it totally uneconomic for anyone with a pencil and piece of paper and the slightest interest in what it costs then per mile to drive.