MPG Issues with 6.2 Denali

[mojo85]

Background: I have a 6.2l Denali running 87 octane gas. Have 2400 miles (3900km) lifetime currently and just did a 1500 mile road trip which consisted of two 700 miles straight drives. Stock showroom tires on it and 2WD the whole way.

 

My question is the DIC gave me a trip MPG of about 17mpg and I noticed it was very very rarely in V4 mode. Is this normal? When I think about it the only time I was in V4 was going down hill. This to me seems pretty high in the mpg category and troubling since where I live gas is much more expensive then the rest of North America. I've been searching around a bit and tried to find an old thread called something like "what mpg are you getting" to compare but no dice.

 

Im getting a bit concerned as most others enter V4 mode at 60-70mph and the only time I do is at city speeds. Also the MPG is higher than most others but can't find much on the 6.2l so i'm honestly not sure. I haven't hand calc'd it.

 

No mods on truck or any other changes other than an infotainment update and trans link check for the recall. Advice?

[Jon A]

Yes, don't run 87 octane in the 6.2. The computer is going to be pulling tons of timing, you're basically in a reduced power mode which is why it can't hold V4 mode like it should.

[mojo85]

Hmm i'm not sure of the availability of the premium gas where i'm moving. I think of the 2 stations one does sell 91 but the other might only be 89 as the highest

[bdbake01]

Dump the 87. Same thing happens in mine if I don't run premium. Automatic -2 mpg or more. Can't hold V4 as it should. It will take about two tanks for full effect.

[fondupot]

that big boy needs premium fuel. Otherwise its gonna be running way less efficient. Get some good top tier premium gas in there.

[Isriam]

you're not gonna make up the difference in mpg vs cost running premium unless you get +3mpg or better. i'm around 16 life on my 6.2 and its not that bad. i also run 87 because premium is more than 20 cents. id consider 89 but i just dont see more than 2mpg difference.

[mojo85]

Cheers for the responses. Made a few phone calls and one of the 2 stations sells the 91 octane so I'm in luck. Its about $6.00 a gallon or 1.60 a litre (see what I mean by expensive where I live?). I have 91 in there now, filled it up last night so lets see how she goes. Regular is $5.26 a gallon or $1.39 for the Canadians playing at home (like me).

 

I'll put 2 tanks through it and report back. I have another 13hr road trip ahead of me Sunday. What cheeses me the most is the dealer told me not to put in the 91 gas, to use the 87. When I brought up that it was recommended, even pointing out the sticker on the inside of the gas cap he was completely confused and said he'd never seen it before. He asked the mechanics who reaffirmed that the 87 was the preferred fuel since 91 would mess with the timing. I have chrome gas cap so I had to pull the stock one out of the box in the back seat to show him but I don't think he's ever seen it before. I guess I should trust the internet more!

[dodgehemi0]

Here is my Denali 4x4 2014 6.2 lifetime

Here is what my last trip netted me

 

 

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[iCryWheniGoPoop]

you're not gonna make up the difference in mpg vs cost running premium unless you get +3mpg or better. i'm around 16 life on my 6.2 and its not that bad. i also run 87 because premium is more than 20 cents. id consider 89 but i just dont see more than 2mpg difference.

 

WRONG! He has a 6.2! It needs premium! If you have a 14 6.2, I advise the same

[Isriam]

i disagree but whatever. ive done real world mpg comparisons between the two and will stick with 87.

[TJay74]

Sounds like this dealer has a bunch of idiots working for it, the truck is designed to run 91/93. Members have already shown the 5.3 should be running premium as well with the amount of knock the 5.3's are showing when logged. It says it in the owners manual and on the gas cap, then to tell you it will mess with the timing. Why yes it will, if you run 87 it will reduce the timing and put the truck in the low octane map and reduce power.

[mojo85]

Just from about 45min in city driving i've noticed it holds V4 much better and at higher speeds with 91 octane. This is the first tank of 91 octane i've had in her. She held V4 at about 90km/h (55mph??) where before that would never occur.

 

Being a truck novice and before this all I really knew about them was they got you from point A to point B and on weekends Point C will the 87 hurt the engine or just reduce power? I ask because due to my isolation I know potentially 91 gas may not be available, in fact i've gone to the store and milk/eggs/bread hasn't been available for 4-5 days.

[dodgehemi0]

Just from about 45min in city driving i've noticed it holds V4 much better and at higher speeds with 91 octane. This is the first tank of 91 octane i've had in her. She held V4 at about 90km/h (55mph??) where before that would never occur.

 

Being a truck novice and before this all I really knew about them was they got you from point A to point B and on weekends Point C will the 87 hurt the engine or just reduce power? I ask because due to my isolation I know potentially 91 gas may not be available, in fact i've gone to the store and milk/eggs/bread hasn't been available for 4-5 days.

Where the hell do you live buddy? Not being a dick

 

 

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[mojo85]

Where the hell do you live buddy? Not being a dick

 

 

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Northern Canada

[iCryWheniGoPoop]

you're not gonna make up the difference in mpg vs cost running premium unless you get +3mpg or better. i'm around 16 life on my 6.2 and its not that bad. i also run 87 because premium is more than 20 cents. id consider 89 but i just dont see more than 2mpg difference.

 

WRONG! He has a 6.2! It needs premium! If you have a 14 6.2, I advise the same