Run a tank of 91+ in your 6.0.

Cowpie · June 18, 2016

Well, it could require more octane to offset a knock situation. More often than not, it would not be from the design, but carbon build up on pistons that could cause a corresponding increase in compression ratio. So while using higher octane to cure a situation does not resolve the conditions that are causing it. The stock design of the L96 6.0L is fine for using 87 regular. But a poor quality fuel or some other factor could lead to carbon deposits building up and subsequent knock situation. Any motor I have that is designed for 87, and then needs higher octane, time for a de-carbon job.

RNGRBOB · November 14, 2016

Would having a Blackbear tune and running the 91/93 octane give you any additional performance or gas mileage? or is getting one of those aftermarket tunes simply snake oil?

Sledge8 · November 14, 2016

Would having a Blackbear tune and running the 91/93 octane give you any additional performance or gas mileage? or is getting one of those aftermarket tunes simply snake oil?

Blackbear and others can tune for 87, 89, 91, E85, etc. In each case they may add or subtract fuel and or timing in all areas of the rpm range to see the potential gains in performance. They also look at transmission tuning and Torque Management settings with the ecm and tcm to suit your needs. This kind of tuning is not snake oil and can lead to a big performance differences. I have heard from them that the L96 is on the high side for compression for them to tune with 87 so they recommend at least 89 for their tuning.

wandern · November 14, 2016

I thought I'd make a notation on this thread.

I record my fuel consumption with every fill up, and have found that my highway gas mileage increases substantially (10-15%) when filling up with premium gas.

Wait!, you say- that's impossible. Premium gas doesn't increase fuel economy. Yes- wait.

I tend to drive in hilly and mountainous terrain, often heavily loaded (4000+ lbs of payload) and with 87 octane fuel, the truck is constantly shifting out of overdrive to maintain speed on slight grades. I will often compensate (when not using cruise control) by allowing the truck to slowly lose speed going up the grade, and regaining the speed once on a level or downhill grade, which will net me a 15-20% increase in fuel economy at the expense of constantly babying the throttle, the inability to keep up with traffic, and the impossibility of using cruise control.

The truck seems to be able to make just enough additional power with 91 octane fuel that it does not need to downshift to maintain speed. I can run several hundred miles on cruise without the truck downshifting once with 91 octane gas in the tank, whereas the truck probably racks up several hundred downshifts with 87 octane.

On longer trips (200-400 miles) that involve primarily interstate and highway travel, I've run both with cruise control engaged, and when manually controlling the throttle with the accelerator (but maintaining a constant speed up grades). In both cases, my unloaded gas mileage has gone from the 12.5-13mpg range to 13.5-15mpg. I was stunned the first time I got almost 16mpg with 91 octane. When hauling a high profile truck camper, my mileage goes from about 7.5mpg to almost 9mpg with premium fuel on the same routes. I have never seen 15mpg with 87 octane gas over the 20,000 miles I've logged with this truck.

In town, my fuel economy is essentially the same regardless of what octane fuel I use- perhaps 2-3% less (well within the margin of error) with premium gasoline.

After seeing the hard data (over thousands of miles on multiple trips on the same terrain in similar conditions), I've started fueling the truck with 91 octane gas when I'm going to be doing long highway trips. For normal around town and mixed usage, I put in 87 and call it good.

For comparison purposes, my 2014 Silverado 1500 would handily return 21-22mpg on the same terrain (unloaded) and on long flatland runs, was capable of returning very close to 24mpg.

revrnd · November 15, 2016

The only reason to run 91 or 93 is if you have high compression. Other than that it isn't doing anything for you.

In the "old days, if an engine was 9.7:1 you had to use premium. GM doesn't say anything about the trucks requiring it w/ that CR. Like some of the posters have said, the mileage would have to increase greatly to make it worth my while.

Kind of like a person that buys a diesel that doesn't tow, trying to justify the purchase by saying the mileage is better (not taking into account the higher purchase & maintenance costs).

Cowpie · November 15, 2016

yes, it can happen sometimes that there is a mpg increase using premium. But if it still costs more per mile, what is the benefit? 10-15% increase is substantial when it is costing more per mile to do it?

Right now in my area, 87 is running about $1.95. Premium is going for an average of $2.56, for roughly a 60 cent spread.

Now if I were getting 15 mpg with 87, for a per mile cost of 13 cents, I would have to get almost 20 mpg, or a 33% increase in fuel economy with premium.... just to break even on the cost per mile. 10-15% better fuel economy, even 20%, isn't going to cut it. I know, it feels good to see an improved mpg, but it is actually costing more per mile so in reality it is a negative. For there to be any appreciable benefit to running premium, the cost spread would have to be only about 30 cents compared to 87. It might be that in some areas, but not in mine.

Very few people actually take the time to run the numbers and see how what they are doing is actually affecting their wallet.

Edited November 15, 2016 by Cowpie

wandern · November 15, 2016

87 octane: $2.80

91 octane: $3.00

Price premium: 7%

Cowpie · November 16, 2016

Now that is pretty good! Haven't seen that tight of a price margin in quite a while. Only bad thing about it is that your 87 octane is about 20 cents a gallon higher than our premium.

Edited November 16, 2016 by Cowpie

Colossus · November 16, 2016

We have

85 @ $2.00 a gallon

87 @ 2.17 a gallon

91 @ 2.30 a gallon

Diesel @ 2.35 a gallon. Is that 2.80 a gallon up in Canada or something?

revrnd · November 16, 2016

We have

85 @ $2.00 a gallon

87 @ 2.17 a gallon

91 @ 2.30 a gallon

Diesel @ 2.35 a gallon. Is that 2.80 a gallon up in Canada or something?

Actually a US gallon is 4/5s the size of our old "Imperial" gallon & our dollar is worth about 73 cents US. (You don't want to know what we're paying for fuel up here)

When the country went metric the powers to be decided that going from mpg to km/L would be too simple (Divide kilometers traveled by liters used). As a result our beloved federal gov't decide that "fuel consumption" would be the measure of a vehicle's efficiency. It is measured as Z L/100 km. Therefore a vehicle may use 10 liters to go 100 kilometers.

"Divide distance traveled by 100 = A"

"Divide liters used by A = X L/100 kms"

MORONS!

Edited November 16, 2016 by revrnd

j-ten-ner · January 28, 2017

Lol..you're making it more complicated than it is.

Take the Liters of fuel used, move the decimal point 2x to the right and divide it by the traveled distance.

so long

j-ten-ner

sdeeter19555 · January 29, 2017

I'll only throw out an experience I had...

I pull Seven Mountains on 322 between Harrisburg and State College quite often. Pulling my trailer (fixed weight of about 5k pounds) on 87 octane, the truck fell flat on its face just like someone was limiting the throttle at a certain point...pedal at WOT, no further power, and slowly lost speed. Same route, same trailer, 93 octane, and it pulled that same hill harder and not only maintained speed but also accelerated. Mostly the same ambient conditions...not enough difference between them to make a significant difference.

Just an experience I had, and the only real difference was the octane of the fuel. Did I get a bad batch of 87? Maybe...

PS:

I wanted to add that when it ran out of power on that hill, it felt like someone reduced the power or pulled the power back. I was expecting a CEL to be thrown because of how badly it pulled the power off, but it dropped to about 45mph and settled in for the drag with no codes. I even mentally scanned all my parameters on the Insight figuring something was hot and that it was a self-preservation thing, but everything was normal.

The next trip with 93, I was able to maintain 55mph and even drop a gear and pick up speed to confidently pull into the passing lane.

I've even pulled fairly heavy up that hill since, and had no issue holding 55mph. But I haven't ran 87 when towing since that day I had an issue.

If anyone has pulled that Seven Mountains, it's fairly steep with several sharp turns limiting speed buildup and kills momentum, and right at the top it has a near 90 degree turn and gets real steep. Most loaded semis struggle to pull this hill much over 20mph, some I could walk faster. It's one that will show you what kind of tow vehicle you have...

Sent from my SAMSUNG-SM-G900A using Tapatalk

Edited January 29, 2017 by sdeeter19555

Doug Rosewood · February 2, 2017

I've always been told its all in your head running higher octane in an engine that isen't designed for it..or tuned for it. To each their own, blue to you, might be green to me..all in the head

tooch420 · February 2, 2017

Look, the bottom line is if you wanted to get good gas mileage you should'nt have bought a 2500! LOL

redwngr · February 2, 2017

Actually a US gallon is 4/5s the size of our old "Imperial" gallon & our dollar is worth about 73 cents US. (You don't want to know what we're paying for fuel up here)

When the country went metric the powers to be decided that going from mpg to km/L would be too simple (Divide kilometers traveled by liters used). As a result our beloved federal gov't decide that "fuel consumption" would be the measure of a vehicle's efficiency. It is measured as Z L/100 km. Therefore a vehicle may use 10 liters to go 100 kilometers.

"Divide distance traveled by 100 = A"

"Divide liters used by A = X L/100 kms"

MORONS!

Lol..you're making it more complicated than it is.

Take the Liters of fuel used, move the decimal point 2x to the right and divide it by the traveled distance.

so long

j-ten-ner

Or just set the dic to read in gallons/miles. (it will be usgall/usmpg, not imp units)