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Discussion Starter · #1 · (Edited)
Went back to regular gas.....

I've been away for a while. Thought I would post an update.

Got to say, I had bad knocking/chugging/transmission issues when I first purchased the truck. Dealer filled it with regular. I decided to go premium on tank #2 and the issue seemed to resolve itself. After nearly a year, I decided to try out some regular again and honestly, I can tell absolutely zero diffs (and my MPG on this tank actually came out better for whatever reason by 1.5MPG).

I know I was an advocate of premium when I first got my truck, but now I'm kind of pissed I've been paying extra for premium with no real benefit. Perhaps the truck's computer "learned" what it needed to. Perhaps I just got used to driving a truck with chuggle issues. I dont know.

But for the guys using premium, go back to regular and see if you can tell any diffs and make up your own mind. You may be able to save some hard earned $.
 

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No need to run premium in these trucks. Mid grade maybe, but 87 from top tier stations is more than sufficient.
Same here. I've always run 87 (Top Tier) in my Chevy trucks and suv's.
 

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Maybe it was just the correct time of day BUT.........


On a recent trip cross country I had occasion to consider and use 86 octane, which is a "norm" in some of the high elevation of western states. In the station I noticed a good number of vehicle owner's filling with the 86 octane in vehicles I was sure required 87 and higher. So I thought what the hell. After about 75 miles I noticed a power and response difference and became concerned, even though no spark knock was noticeable.

At about 125 miles, I decided to top the tank with 91 octane and pulled into the station and "stuffed" 5 gallons of 91 into the tank. I set the DIC to the "A" log (which had recorded, an indicated, 23.5 MPG) and reset the values. I also set the Cruise Control to 70 MPH which was my norm for the Interstate trip. I constantly reviewed the MPG as I drove and watched as in steadily climbed to 33.5 MPG for 200 miles....at which time, I started a decent from the mountains to the desert, approximately 98 miles, registering a final 29.4 mpg for the fuel used since the last fill up.


Quite surprising, is it not? an anomaly? or are these vehicles capable of recognizing this kind of mileage under perfect conditions? You owners in areas where 86 octane is available, do you use it, or step up to the next available grade, generally 88 octane?
 

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I run premium in mine solely as I can get it without ethanol in it. Otherwise, I wouldn't care.
 

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Here is how you need to look at this. Bond of us can measure accurately mpg precise enough to compare numbers of 1 to 2 mpg.

We do not measure flow, how much we put in each time equally and driving conditions constantly change in Terrain, temps and traffic.

This not criticism of anyone but just the reality of mpg ratings are normally done in lab conditions and with precise equipment none of us have.

With that said one thing we need to also consider MFGs are desperate for mpg to meet goverment mandated regulation. So if a vehicle could pick up 1.5 mpg with just premium then one would think they would reckoned this across the board vs spending millions to redesign cars, engines and all the other things like AFM and hybrids.

There was a time premium fuels did have more cleaners and anti deposit additives but today with top tiers they all now have the same additives.

The only thing higher octain does is prevent pre ignition in cars of higher compression and or super/Turbo charged applications.

Tunes are a different ball game as that is up to the tuner to pick up a few HP they will move some things like the knock retard and timing. The big results are left for super and Turbo applications wher boost can be moved. That is why my old 2.0 Turbo went from recomended to required when the boost went from 15 psi to 23 psi. It netted 55 hp with just a tune and two maps.

As for ethanol in fuels much of this depends where you live and what time of year it is. Much of it is in al, fuels where mandated by the EPA. Also top tier fuels will limit it to where is is mandated. If you are one that can buy with out any count you some of the lucky and few.

The bottom line is try to use a top tier and if you have not added a tune regular will deliver as good of performance as any other fuel you can use.

Bigger is not always better
 

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From what I have read, the EPA uses their own blend, similar to premium, to verify fuel economy tests (when they bother to do so). So in that regard, depending on the vehicle, it could make a difference if it netted an overall gain in power (such as, for example, my wife's ecoboost mustang that even Ford admits makes more power on premium, despite recommending regular).

Biggest difference in daily driving though, in our experience, is fuel quality. Not octane. We run regular knowing the vehicles were designed for it. I will run premium in hers, with adequate changeover time, if driving hard, which is rare. I run plus in my older car that just wasn't designed for ethanol gas and 100 degree temps, because then it doesn't ping. But overall, agreed on running what the manual says.

Interesting info on your personal experience. Kind of rings of a tank of poor fuel combined with a truck that still had some learning to do
 

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In my 2017 Colorado with the LGZ 3.6L V6 I'll be staying with regular 89 octane. I have tried 2 fillups in a row using non alcohol 91 octane and noted no difference in MPG or performance to speak of.

Now there is evidence that the ECM in the previous LFX 3.6L V6 to suggest that using premium with provide a bit more performance if it is used regularly. A fellow on another forum who does programming for GM ECM stated that the LFX V6 will adjust and create or use a different internal tuning table for air/fuel ratio. It will not result in higher MPG necessarily. . . just a bit more gusto off the line and in passing gear.

However, he stated it would take 3 or more tank fills to purge out the lower 89 octane fuel and driving with the 91 octane to obtain this result. And if you returned to 89 octane ethanol blend, it would soon revert to the lower performance operating table in the ECM.

This is still not a night an day difference. Using 91 non ethanol in the LFX V6 just gave a bit more kick. I tried in in our other vehicle and it seemed to support what the fellow stated.

That said. . . both the LFZ and LGZ have plenty of output for me. Any little truck that can do sub 7 second 0-60 without a tune is no slouch. My brother who has a 2015 Ford F-150 with the 3.5L twin turbo could not believe the Colorado would do close to 6.1 second 0-60 till I showed him.
 

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I switched over to 91 on my 2016 Equinox with the LFX V6 and noticed a small performance difference but mostly noticed less soot on the dual chrome exhaust tips. If the exhaust tips are staying cleaner, then so should the inside of the engine? I am not putting a huge amount of miles on my 2017 Colorado with the LGZ V6 as I only have a 20 minute commute, mostly on a 4 lane road.
 

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I run premium in mine solely as I can get it without ethanol in it. Otherwise, I wouldn't care.
In that case, you may see some nice mpg gains. Here in Illinois everything has 15% ethanol in it.
 

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In that case, you may see some nice mpg gains. Here in Illinois everything has 15% ethanol in it.
My understanding is that our trucks are only warrantied to 10% Ethanol. The 2015-2016 models at least were not rated for flex fuel, E85, etc.
 

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My understanding is that our trucks are only warrantied to 10% Ethanol. The 2015-2016 models at least were not rated for flex fuel, E85, etc.
Negative, Page 24 in my 2017 owners manual says that everything up to E15 is OK. Anything above E15 is not OK.

E15 is not flex fuel. It is 85% regular gasoline, ant 15% ethanol.

E85 is flex fuel, that is 85% ethanol, 15% regular gasoline.
 

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Most areas use E15 mostly due to the EPA and their requirements on emissions. It is most often put into use in the fall and changed over in the spring. Slight MPG drops are noticed not attributed to colder weather only but more so due to the ethanol content. We see it here due to emission reasons in the winter.


E85 normally is found on vehicles with green gas caps and most also have a label or tag on the back that says flex fuel. They are not as common as of a few years ago.


I noted since DI has come along you do not see as many flex fuel vehicles. I am not sure if there is a connection or the change just happened at the same time.
 

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My understanding is that our trucks are only warrantied to 10% Ethanol. The 2015-2016 models at least were not rated for flex fuel, E85, etc.
Good point. And yup, the owners manual does say 87 octane 15% ethanol is fine.

But No "E15" in the upper midwest here that I have seen. All tanks at statewide location just state "May contain up TO 10% ethanol".
So that implies there may even be less than 10% ethanol in a particular grade of gasoline. Surely no 15%. Must be in more densely populated industrial states and areas.

Glad about no E85 as well.
 

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My truck is more sensitive to ethanol than octane. Runs better with regular and no ethanol vs premium with 10% ethanol. Smoother acceleration and up shifts sooner. Only problem is non ethanol fuel is almost 2X the price.
 
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