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FWIW, we live at 7,500 ft elevation... even with a turbo I kinda doubt that octane makes much difference but I'm not sure about it. This is my first turbo so I've been using mid grade fuel and it seems to do fine. Premium costs about 90 cents/gal more than regular around here.
 

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FWIW, we live at 7,500 ft elevation... even with a turbo I kinda doubt that octane makes much difference but I'm not sure about it. This is my first turbo so I've been using mid grade fuel and it seems to do fine. Premium costs about 90 cents/gal more than regular around here.
Inside your engine, with the turbo spooled up, it's virtually the same as being at sea level. The turbo boosts to a given pressure, regardless of outside atmospheric pressure--that's why turbos and superchargers were put on aircraft when they used recip engines: to maintain power and increase the ceiling altitude. Therefore, high octane is essential regardless of your elevation, in accordance with manufacturer's suggestions, to prevent damage to the engine at high boost/high compression.
 

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I've been running a mix of 91 and 89 since I purchased the truck ('09 Terrain Denali). I will check my millage numbers and report back. I have not attempted to run regular as of yet to see the difference.
 

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Stick with the recommended fuel for a turbo charged motor. It has nothing to do with each individuals mileage and everything to do with the life of the turbo and valves as well. Running a lower octane works with the advanced computer control but it also is sending false signals and may be retarding or advancing your timing incorrectly. In turn this can lead to an overheated turbo.

I have seen one on an Audi red hot and then catching fire. It was not pretty.

I am so glad to have the V6. But please people run the correct fuel in your beautiful GM automobile.
 

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.

This is regarding the 2.0 turbo; the recommended fuel for the 1.5 turbo is regular grade 87 octane.

So far all that I use is Top Tier Phillips 91 octane, no ethanol or BP 93 octane, with ethanol.

I'm just a little gun shy of using 87 octane because of a potential LSPI issue with these direct injected turbo engines: Just not willing to gamble with an engine failure if better fuel can potentially avoid it.

Remember, LSPI is an issue among various manufacturers using small displacement, direct injected, boosted induction engines, and the cause hasn't been completely understood or resolved yet.

I also use a Dexos1, Gen2, certified oil: Mobil1 Extended Performance 5W-30 in my 2019, 2.0 Equinox, to also aid in preventing the LSPI phenomenon.

If the GM powertrain engineers recommend premium fuel, I'm going with that recommendation.

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I only use what is recommended by the manufacturer which is super at 92-94 octane. I average around 40-44 mpg Canadian or 33-37 mpg (us). There are a lot of differences other then mpg for using a top tier premium gasoline, and I spent 50K for a fully loaded Denali, so why would I try and save a couple of dollars with a cheaper gasoline. Just my thoughts.
 

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Well Said. I'm a retired ASE Master Tech. It goes as tharvey57 sort of says. If you have to ask how to save pennies, you bought the wrong vehicle. This reminds me of the guys who buy supercharged jet skis and won't buy the proper fuel. They get towed in off the lake or ocean, motor blown. The computer in the car can only make up for issues for so long, then the possibility of "Kaput" increases. Put your big boy panties on and suck it up!
 

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Well Said. I'm a retired ASE Master Tech. It goes as tharvey57 sort of says. If you have to ask how to save pennies, you bought the wrong vehicle. This reminds me of the guys who buy supercharged jet skis and won't buy the proper fuel. They get towed in off the lake or ocean, motor blown. The computer in the car can only make up for issues for so long, then the possibility of "Kaput" increases. Put your big boy panties on and suck it up!
That is a pretty lame response.

I have commercial heavy trucks. I tweak out even one tenth of a mile better fuel economy when I can. Each tenth nets me a savings of $600-$700 a year is fuel cost savings per truck. Imagine just 1 mpg better mpg. And i always look for the best value is fuel I can get.

Just because someone wants to save some scratch on the operation of their vehicle doesn't mean they bought the wrong one or they have the wrong mindset. As much as ego inflated morons would like to make them think so.

I don't have a turbo engine that is part of this discussion. My personal vehicles are all NA, but I use E85 in my various vehicles since they are flex fuel. 100 Octane and half the price of premium fuel. The 11.2:1 ratio 2.4L LEA in my Nox runs silky smooth on the stuff. The 6.0L in my 2500 can push snow, haul, and tow with the best of them while using E85. And even the diesel 2500 with its better fuel economy cannot come in as low of fuel cost on a per mile basis that I get with E85. And even though E85 delivers lower fuel economy, it also has such a low price in my area that there is not a similar Nox out there that can beat the low cost per mile of operation if they use regular, mid grade, or premium. Now that is putting big boy panties on and sucking it up...... and engaging the brain instead of the ego.
 

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I would go with the manufacturer's recommendation of premium fuel. Would also recommend using premium 100% synthetic oil, meeting API SN+ requirements, in the proper grade with turbo charged engines to help reduce Low Speed Pre-Ignition which can cause severe damage to the engine.
 

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That latter is especially important with a turbo gasser.... preventing LSPI. And that does indeed call for a very good oil. The additive package in that oil is paramount. LSPI is terrible for an engine. Will destroy pistons and valves. And it has been found that the oil plays a part in preventing it.
 
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I run 91 in mine most of the time but, if I come across a station without it I run 93... I bought the 2.0T for it's performance so I want to get the most out of it AND I want to keep this car for the long haul so I want to put the recommended fuel..
 

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The 6.0L in my 2500 can push snow, haul, and tow with the best of them while using E85.
You apparently are pleased with using E85 in your flex fuel vehicles.

You say you push snow with your 6.0, 2500. My question is, do you live in a climate that has extreme cold temperatures in the Winter; and do you use E85 in the cold temperatures without starting/running issues in the cold temperatures?

My only flex fuel vehicle is my 2009 5.3, 1500 Silverado; which has never tasted a drop of E85. It isn't too popular in this area as there isn't enough margin of cost difference to justify its use. My other concern is that due to its limited popularity, the stored fuel may not be fresh.

I also have concerns that a vehicle that has never used E85, and then switched over, may experience fuel system problems due to the higher alcohol content placing more hydrocarbon residue/solubles in suspension.

Your explanation of why you use it makes sense, but I'll probably never use it for my own vehicles.

I'm getting a little off topic here, but I guess it does relate to fuel: To steer this back on topic, I use what fuel is either required or recommended in my turbo engines: The 1.5 turbo in her Malibu gets 87 or 89 octane; my 2.0 turbo in my Equinox gets 91 or 93 octane premium.

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You apparently are pleased with using E85 in your flex fuel vehicles.

You say you push snow with your 6.0, 2500. My question is, do you live in a climate that has extreme cold temperatures in the Winter; and do you use E85 in the cold temperatures without starting/running issues in the cold temperatures?

My only flex fuel vehicle is my 2009 5.3, 1500 Silverado; which has never tasted a drop of E85. It isn't too popular in this area as there isn't enough margin of cost difference to justify its use. My other concern is that due to its limited popularity, the stored fuel may not be fresh.

I also have concerns that a vehicle that has never used E85, and then switched over, may experience fuel system problems due to the higher alcohol content placing more hydrocarbon residue/solubles in suspension.

Your explanation of why you use it makes sense, but I'll probably never use it for my own vehicles.

I'm getting a little off topic here, but I guess it does relate to fuel: To steer this back on topic, I use what fuel is either required or recommended in my turbo engines: The 1.5 turbo in her Malibu gets 87 or 89 octane; my 2.0 turbo in my Equinox gets 91 or 93 octane premium.

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Well, moderately cold. We get some -20F and lower occasionally in the winter, but mostly in the -5F to +10F range. Yes, I use E85 year round.

Now to be somewhat fair here..... E85 actually is blended in various ratios throughout the year in anticipation of weather. In deep winter, it is usually only a minimum of 51%. In summer the blend gets close to the 85% max. It can vary in ratio at different times of the year. Where I live, summer E85 (April thru October) has to have a minimum of 70%. Winter can go down to 51%. And the state boys are pretty meticulous about randomly checking stations to see if they are in compliance.

Even at the lower ratios of ethanol, the pricing has been so favorable that I would be an idiot not to use the stuff. And I have, exclusively for over 2 years now, year round. Even on a 2000 mile round trip to Wyoming last year. Used E85 the entire trip. Stuff is really good at higher elevations, probably because of the higher oxygen content of ethanol.

Well, if you have used E10, and most folks are buying E10 since most of the gasoline in the country is laced with some ethanol, switching to E85 with a flex fuel vehicle should not really be an issue.
 
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We run mid grade 89 octane in ours...only has 6k miles no pinging what so ever, but I have not been through heat of summer with it yet. Time will tell and if I suspect any pre-ignition spark knock or ping I'll be pulling the plugs to confirm if any detonation is occurring. There is no need to guess or finalize choices based on conjecture the plugs will tell ya the story...if ya know how to read em.

PS not the same as it's naturally aspirated V8 our 07 Caddy also has the recommended premium fuel suggestion from GM, we have been running regular 87 octane in that for the last 100K miles with no ill effects :surprise:
 

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If one really wants to know, get a OBD scanner that will display real time while driving and test things. I don't really use it for the topic at hand, but I like the BlueDriver OBD scanner. The module plugs into the port and a bluetooth hookup to my iPhone and I can see all sorts of real time stuff going on.

I think in most cases, mid grade would be a pretty balance for the average person. Many of the folks that have the Silverado 1500 with the 6.2 Ecotec use 89 regularly. And that engine has a premium 91 recommendation. In that case, if really working like hauling heavy, towing, or driving hilly terrain, it probably would be wise to use premium 91. The same thing can be said for these turbo motors we are discussing. If one is really going to put the motor thru its paces, probably best to use 91. But for average day to day stuff, 89 should do the trick. Especially if there is a substantial price difference.

And Low Speed Pre Ignition (LSPI) is a common thing with these newer high compression, direct injection motors. It is the primary reason that led to improving the API SN rating on motor oil to API SN+. One doesn't want to risk beating the snot out of their motor and killing it prematurely with LSPI. Running regular should only be used when there is no other choice.

My 2017 2.4L LEA is not turbo, but it does have DI and it has a compression ratio of 11.2:1, darn close to the ratio of the Ecotec 6.2 which GM says should use 91. I would not consider running 87 in it on a regular basis. I use E85 because of the big price advantage, and it has a killer octane rating, but if I was using gasoline it would be mid grade 89. LSPI can affect the LEA 2.4L engine too just like it can affect the 6.2L, not just the turbo engines. Anything running higher compression ratios and direct injection is fair game for LSPI.
 
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Copperhead--Agree completely. Regarding LSPI, seems that GM is leading us down that path with the 2.0T and 9-speed transmission that shifts into 9th at speeds as low as 60 mph and 1400 rpm. I encounter those conditions routinely in city freeway driving. Small amounts of throttle input don't always cause transmission to kick down, but does create idle situation for LSPI. I would rather err on side of caution; therefore I use premium with higher octane.
 

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That is the reason I am fond of using manual mode for most of my driving. That includes my pickup as well as my Nox. I want a little more control on keeping the engine in the optimal power band. And in doing so, I have not seen a hit on mpg. I think that is primarily due to the fact that on the rolling hills in my area, by using manual mode and keeping RPM's as a reasonable level on the engine, it greatly reduces the shifting and gear hunting that goes on by the trans when it is left to its own. That constant shifting on every little mole hill really takes a toll on fuel economy and transmission longevity. This gear fast, run low concept is nice on a test track and makes the numbers more palatable to corporate and government interests, but is doesn't equate well to real world operation. At least there is manual mode.

Peak torque on the 2.0T is at 2500 RPM. it really rises fast below 2500 (or one could say "falls fast" below 2500 if the trans is kicking into higher gears sooner), holds it well up to 4000 RPM, then tapers downward above that. 90% torque is available at roughly 2000 RPM. That should give an indication fo were the engine should be operated. On my 2.4L, the torque curve is more gradual across the spectrum but I get 90% torque at around 2100. So for most of my rolling hill stuff, I keep the RPM's at or above 2100. Only if I am on flat ground with constant speed and low load will I let it stay below 2000 RPM for any period.

I basically use the same principle regarding torque as I use for my heavy commercial trucks. It has served me well as a good operational technique for many years.
 
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Copperhead--you're a man with the same philosophies as me. My father drove 18 wheelers and taught me the same principles you just wrote. Hitting that optimal part of the torque band is essential to performance, longevity, and fuel economy. thanks for sharing and reminding me of those good days of "rowing twin sticks".
 

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Most welcome. Yeah, many really don't take the time to get a handle on these concepts. No one ever really showed this methodology to them so they never really learned of it. Not their fault, so I can't really chastise anyone if they don't agree.

And shifting 18 gears in a semi truck for over 5 million miles, I have picked up a few concepts along the way that really are applicable to any vehicle. Some things just are common to all motors. Diesel or gas, large or small, the concepts are the same.
 
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PS; Did you know, that the crankcase gases that go thru your PCV, & back into your intake is loaded with oil molecules that lower your octane rating? All those oily air streams burn, coat your valves & pistons with carbon? The solution is a Air/Oil Separator, then you get clean air & NO carbon build-up & get the octane you paid for!
 

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I'm using premium. With this high compression, small displacement turbo charged engine and the transmissions tendency to shift to 9th ASAP I don't want to risk low speed pre ignition which has been a thorn in the side of this type of engine. I will also do oil and filter changes before the oil life indicator says it's time and of course use full synthetic with the appropriate ratings.
 
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