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Went bag to regular gas.....

23K views 130 replies 44 participants last post by  klaborde 
#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 $.
 
#7 ·
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?
 
#45 ·
I live in colorado and 85 is the low grade here. It sucks. The computer in just about everything will detune a slight amount. Manufacturers are no longer saying it's ok to do in higher elevation. I always run 87 or 89, whichever is the mid grade. I only run top tier. You can easily tell the difference in n/a engine's. I wouldn't ever run below recommended minimums in anything forced induction, especially nowadays. The computers usually will adjust to increase pressure anyway.

Sent from my SM-G950U using Tapatalk
 
#8 ·
I run premium in mine solely as I can get it without ethanol in it. Otherwise, I wouldn't care.
 
#9 ·
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
 
#10 ·
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
 
#12 · (Edited)
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.
 
#13 ·
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.
 
#18 ·
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.
 
#20 ·
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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#21 ·


It's become more commonly available here (Non-ethanol fuel). I use it in all my lawn equipment, motorcycles and sports cars.
My DD is whatever I can get on the cheap. It sucks to get worse fuel mileage and a little less performance with E10 vs. non-ethanol, but it's not worth the extra coin.
 
#22 ·
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 $.
Don't count your chickens before they hatch...... How long has it been since you switched back over to 87?? Give it some time - you might be back to buying 93 again in a couple months.

The computer is constantly learning, but from what I've experienced..... Those changes aren't drastic enough for you to notice until they gradually get worse after a couple months.

I don't know where you're from - but colder temps are upon us and 'winter gas' is coming. That might change things for better or worse. I can't remember how mine acted like last winter. I have PC and usually run 89 and the chuggle has been good. That is.....until we bought a boat and have been towing that around every weekend (we don't always use tow/haul mode). I think my truck gets confused. LOL

We use non-ethanol in the boat. We have to drive 20-30 miles to get it.....
 
#24 ·
I stay with 89 (mid grade). I tried 87 as well as 91 for a few tanks in a row and noticed my mpg go up as the grade increased, for the way I drive, performance was about equal.
I looked at cost per mile, and 89 came out a few cents cheaper. Quebec has to have the most expensive gas around, $1.35+ per litre (5.10/gal if I did my math right)
 
#26 ·
Owners manual recommends a "TOP TIER" and refer you to Home | Top Tier Gas. Basically any major brand name fuel, minimum of 87 octane regular unleaded. Not more than 15% ethanol.
 
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#28 ·
When towing the TT I fill up with 91 octane. When light the Z71 gets 87 but alternate to achieve an average 89. I have been doing this for 2.5 years and no pinging, chuggle, farts....etc..etc...I try to keep the ethanol below 5% and really don't care about gas mileage as it is a truck and does what I purchased it to do without much effort.
 
#31 ·
Top Tier is a license you would be surprised how many brands have the Top Tier license. It is much like the oil that has the Dexos license. Here is a list of Top Tier licensed gasoline brands. Licensed Brands | Top Tier Gas
51
 
#32 ·
I just returned from a trip to Texas with my Canyon loaded with approximately 1000 pounds of people and cargo, on the 4400 mile round trip the truck averaged 25.5 mpg with a high of 28 on one tank. The route is from Washington State through mountainous Idaho, Montana, Wyoming, Colorado and onto flatter New Mexico and Texas, I filled with the lowest grade at the pump and never felt a need for more power and no knocking or other abnormalities.
I make this trip each year and each of my last three Canyon's has delivered mileage in the 25-26 overall average ( both five cylinder and V6) all on regular level gasoline as is recommended in the manual.
 
#33 ·
I cannot comment in much detail, however, if you are paying for anything but 87 in any car that is rated for regular you are wasting your money. Whether it be a Ford, Toyota, GM product. It doesn't matter. Mid-grade is the largest scam next to Nigerian Princes calling your CG ad's. Don't use it; you are wasting your money, you don't make more power or help the engine at all. If you are concerned about knocking, don't be. It is all tried and true. The largest issue that you will ever have in an engine are machining flaws or inclusions in parts that lead to premature failures. Calibrations are developed and testing in the field and dynos for years before a customer gets their hands on it. Unless you are running a tune that specifies a fuel to use stop wasting your money. Premium is $1 more these days and the only thing it will ever help you with is draining your wallet. The amount of octane that premium benefits is not enough to warrant using in a naturally aspirated engine. Maybe if on a 95+ day and you are towing max loads I could see a benefit, but DD driving you won't stress the engine or cal enough to ever warrant the blatant waste of money from using premium. *end rant*
 
#34 ·
I'm gonna have to disagree. I had some knocking and took my truck in to the dealership who proceeded to hook it up to their computer and record data as we drove around. The data was then sent to GM to look into. In the meantime I tried out 94 octane gas and my knocking immediately went away and the sluggishness in low gears also went away. A couple weeks later the dealership called me back and said the GM tech's recommend trying premium gas. Many people on here have experienced better acceleration and no more chuggle after switching to premium. My truck is now much more enjoyable to drive now that i have seotched to premium. I also doubt GM would recommend it as a fix if it doesn't make a difference.
 
#35 · (Edited)
Wow, 2 pages of misinformation, speculation, and zero technical discussion. If you aren't at MBT and there is dynamic timing left on the table, you will benefit from premium. As for the OP knocking with 87, that's indicative of: a poorly tuned knock sensor, a bad knock sensor, a bad knock strategy, an otherwise unidentified lean condition, or terribly awful fuel, among other possibilities. As for ethanol, as long as you are driving your truck frequently and refilling fuel frequently, you'll never have a problem. E15 must be labeled as E15, you'll never get E15 in regular unlabeled fuel. E15 is usually 88 octane and a few cents cheaper. Small or carburetor engines that sit for weeks will absolutely get gunked up or worse.
 
#36 ·
Thank you sir. If your 87 IS knocking, you won't hear it, the knock sensor will tell the computer to retard the timing more and as a result, your acceleration will be slower, or your towing will be with less power. Premium isn't more explosive, it burns SLOWER. Most tunes on the market simply advance your timing to take advantage of premiums slower burn. While premium won't make your 87 vehicle faster, (without a tune), it WILL keep the gas from causing any possible timing issues like knocking and slowing your truck down.

At least this is what I think and I stayed at a Holiday Inn Express last night.
 
#37 ·
Today if you have knock issue and if the knock sensor is not taking it out you will get a check engine light. There is no hiding it.

Odds if you get a light you have an issue with a sensor or other problem that needs corrected as GM spends a lot of time to maximize the performance on regular fuel as not to turn off buyers who do not want to pay more for High Test.

This is why most Supercharged and Turbo engines are premium recommended and not required anymore. Chevy was mad when they got stuck with the Premium Required second gen 3800 SC for the Impala and Monte SS when Pontiac got the Gen 3 that would run on either regular or premium. I was at the home of the Marketing director and he was very concerned how it would effect sales. They want to leave the choice to the customer and not hurt sales. The choice a little more for gas or Approx. 25HP in most cases.


There is more timing there if you are willing to move up in fuel but the gains are small unless it is Turbo or Supercharged. The MPG gains are non existent in most cases.

If the gains were significant they would have gone full premium long before spending millions for AFM and other tricks to pick up a MPG or two.
 
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