# Some clarification.....Octane and colder temperatures....



## 6Speed2016LT (Jun 14, 2016)

I know there has been much talk in the past about using high octane gas (91+) if possible to help mitigate LSPI from occurring. With temperatures dropping here in Canada (Mid 30's today, around 4C) 

Is there any advantage at all to going back to 87 Octane other then saving a few bucks?

Would you guys continue using a higher octane gas or is it completely unnecessary with colder weather?
I can say I put 87 in my tank on my last fill up (was pretty much empty) and I am noticing a drop in fuel economy...

Jason


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## JLL (Sep 12, 2017)

It all depends if you think the risk of LSPI is work saving a few bucks. Only you can answer that question.


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## snowwy66 (Nov 5, 2017)

I run 91 year round.

I'm not taking chances.


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## Barry Allen (Apr 18, 2018)

What is the cost split and where does mid-grade (89 octane) fall on the cost spectrum?

Mid-grade gasoline has always existed in this weird bizarro world. Like, seriously, who buys it? The only vehicles I've ever heard of using it (and this was a surprise to me to find this out about a year ago) are Chrysler vehicles with the Hemi engine. I guess the Hemi V-8 engines that are naturally aspirated call for 89 octane in the owner's manual. Who knew? ¯\_(ツ)_/¯ 

Anyways, there are some pricing anomalies around me. There are stations where regular is (examples) $2.99, mid-grade is $3.09, and then premium without ethanol jumps to $3.59. There are also a few stations selling the newer E15 blend that is 88 octane, and it sells for about 3-5 ¢ cheaper than 87 octane. Also unique to my area is one fuel station where I could buy E10, E15, E30, E50, and E85. With my prior Hyundai I would fill up on E30 for cheaper and the fuel economy difference was almost nothing. I can assume the octane of E30 was above 91, but there was no label on the pump.

So, what is the price of mid-grade? Is it exactly between regular and premium, or is there a price discrepancy where it falls about 20% above regular but 80% below premium?


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## Barry Allen (Apr 18, 2018)

Quick question: Is your car a Generation 2 Cruze?

If so, have you had the ECU update done at the dealership, to prevent cracked pistons?


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## 6Speed2016LT (Jun 14, 2016)

Barry Allen said:


> Quick question: Is your car a Generation 2 Cruze?
> 
> If so, have you had the ECU update done at the dealership, to prevent cracked pistons?


Yeah its a Gen 2.......March build date of 2016. In the first few years I always just ran 87....Then after becoming educated I started using 91 to 94 depending what station I was filling up at. Also using 5w-30 Amsoil.........

No I have not had the ECU update yet as I have had no reason to take my car in to the dealer. Maybe I should pay for the hours labour and just get it done.....

I just remember reading somewhere that the high octane has was way more important in the summer months then in winter because of the temperature.....I could be wrong.

Jason


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## Blasirl (Mar 31, 2015)

6Speed2016LT said:


> I know there has been much talk in the past about using high octane gas (91+) if possible to help mitigate LSPI from occurring. With temperatures dropping here in Canada (Mid 30's today, around 4C)
> 
> Is there any advantage at all to going back to 87 Octane other then saving a few bucks?
> 
> ...


If you have not modified your vehicle and do not make a habit of getting on the throttle, then 87 octane year round should not be an issue. I would still get the ECU update though. IF you happen to get some knock at times, bump up to 89 and see if that helps. If not continue to up the grade until it stops. If on the other hand you do a lot of towing and other types of driving that may cause lugging, then you need to be more concerned about LSPI. You could start by using an oil formulated to combat LSPI. I personally use Amsoil.

Do to my driving style and my modifications, I use 93 year round.




Barry Allen said:


> Mid-grade gasoline has always existed in this weird bizarro world. Like, seriously, who buys it? The only vehicles I've ever heard of using it (and this was a surprise to me to find this out about a year ago) are Chrysler vehicles with the Hemi engine. I guess the Hemi V-8 engines that are naturally aspirated call for 89 octane in the owner's manual. Who knew? ¯\_(ツ)_/¯


It probably has to do with the compression ratio.


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## Johnny B (Jun 4, 2019)

LSPI is sort of hard to find solid info on. It seems car manufacturers are purposely not being transparent on the issue. Anyway, in my opinion using Dexos 1 Gen 2 oil ( with the GF-6 and SP ratings) is really the best preventative measure. Other oils might be great lubricants but if they use a lot of calcium that isn't good for LSPI and if it has to much ZDDP it will poison your converter. In short (hint hint) a more additive oil isn't always better.


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## 6Speed2016LT (Jun 14, 2016)

Johnny B said:


> LSPI is sort of hard to find solid info on. It seems car manufacturers are purposely not being transparent on the issue. Anyway, in my opinion using Dexos 1 Gen 2 oil ( with the GF-6 and SP ratings) is really the best preventative measure. Other oils might be great lubricants but if they use a lot of calcium that isn't good for LSPI and if it has to much ZDDP it will poison your converter. In short (hint hint) a more additive oil isn't always better.


I hear you on that one.......I know there are a lot of Amsoil guys here with apparent tests to back it up that it prevented LSPI in all tests....So I went with that. Who knows anymore..

Jason


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## Thebigzeus (Dec 2, 2018)

Blasirl said:


> Do to my driving style and my modifications, I use 93 year round.


🤠


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## Barry Allen (Apr 18, 2018)

Blasirl said:


> It probably has to do with the compression ratio.


Oh, for sure. The vehicles run fine on 87 octane, though.

On second thought, I do recall that the Dodge V-10 engine is one that suggested 89 octane.


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## JLL (Sep 12, 2017)

Out of curiosity @Blasirl , what kind of a low compression ratio are you speaking of?


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## Blasirl (Mar 31, 2015)

JLL said:


> Out of curiosity @Blasirl , what kind of a low compression ratio are you speaking of?


QUE! NO Entiendo.


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## Barry Allen (Apr 18, 2018)

6Speed2016LT said:


> I just remember reading somewhere that the high octane has was way more important in the summer months then in winter because of the temperature


That might have been something I said here.

In winter, you have very cool air flowing across the intercooler. The charge air cooler can function well to keep intake temperatures low and reduce the chance of knocking or pre-ignition and you can probably drive the car just fine with mid-grade fuel. I don't have any equipment to monitor engine parameters to test this, though.

In summer, hot ambient temperatures are where any turbocharged/intercooled engine struggles to perform. You get higher air intake temperatures and then you have warmer air flowing across the charge air cooler, meaning it can't possibly perform as well as in cool ambient temperatures.


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## jblackburn (Apr 14, 2012)

The difference on 87 is so noticeable in my car that even my wife noticed when she put the "wrong" octane in it and acceleration was laggy and hiccupy. 

It runs like crap any time of the year on anything <91. My Gen 1 was far more tolerant of 89 in winter months.

Our friends have Ford Ecoboost 2.0's that don't care what swill you put in the tank; they just tend to rev quite a bit higher than the 1.4T (and get way worse MPG).


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## CRUZE-66 (May 4, 2019)

The rundown for me is this; with my DI Gen2 Cruze I don't want it to go to the 87 octane fuel map. Why? Because 87 octane means pulling timing and enrichening the fuel mixture to help cool things. I don't want extra fuel in there. 

When the combustion chambers are real hot and there's extra fuel floating around the crankcase, ring lands etc. and you have oil loaded with metallic compounds like calcium, plus old oil will have plenty of wear metals like aluminum, iron and copper - guess what can happpen next? ...Fuel vapors galore, a super hot engine and all kinds of super hot metallic particles. BAM! 

One of the oil additive companies even said the octane of the fuel in these circumstances might not even matter. Part of the problem pointed to certain components in gasoline, regardless of octane, were more prone to LSPI events. Which means the refineries likely played a role in LSPI prevention over the last several years along with engine oils(SN+,SP) and tweaked engine tunes. I read recently that Shell has a patent on a anti-LSPI fuel. I'm not sure if it's the additive package, the refinery process or both. But you really don't hear about blown engines from LSPI to any degree like you did 4 or 5 years ago.

What it means is you want to keep the crank case clear of fuel vapor as much as possible especially since DI is more problmatic than port injection. So higher octane to resist preignition and leaner A/F mixtures.

Next, the ethanol comes in with hot weather when you want to keep the combustion temps down as much as possible. Around 90F+ everything is going to be hot. The alcohol will help counter everything being heat-soaked. It amazes me how hard and smooth the car pulls in 90F+ temps with 93 octane and a gallon or so of e85 added.

But that same alcohol can quench the combustion chambers too much during super cold ambient temps when used as a daily driver. Last winter I noticed a bit of a gassy smell when checking the oil. I figured it was time to stop juicing with a gallon of e85. In January I need more heat in the cylinders, not less. But I'm not going to go to lower octane because of the potential fuel map switch like I stated above. Other than super cold weather though, I'm still juicing e85.

The next peice of this puzzle is how to try and get as complete combustion as possible, regardless of how lean the mixture is, to further minimize blow-by, excess fuel vapors and soot.

But as has been noted already, with all the mitigations done with LSPI you're probably fine with 87 octane. Especially in the winter and likely the summer too. And also as noted it depends how much that extra insurance the higher octane is worth to you.


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## 17Cruzer (Apr 18, 2017)

Barry Allen said:


> Quick question: Is your car a Generation 2 Cruze?
> 
> If so, have you had the ECU update done at the dealership, to prevent cracked pistons?


Had the ECU updated awhile ago, noticed a decrease in fuel economy.


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## Barry Allen (Apr 18, 2018)

17Cruzer said:


> Had the ECU updated awhile ago, noticed a decrease in fuel economy.


That doesn't surprise me. The original tune probably eeked as much efficiency out of the drivetrain as possible and then we ran into LSPI problems. After that, the tune is a bit less aggressive on efficiency at the expense of fuel economy.

Notice that any updates won't have to go through the government fuel economy tests to have the MPG ratings restated. Nope, nothing to see here, move along now.


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## 17Cruzer (Apr 18, 2017)

Barry Allen said:


> That doesn't surprise me. The original tune probably eeked as much efficiency out of the drivetrain as possible and then we ran into LSPI problems. After that, the tune is a bit less aggressive on efficiency at the expense of fuel economy.
> 
> Notice that any updates won't have to go through the government fuel economy tests to have the MPG ratings restated. Nope, nothing to see here, move along now.


The decrease in fuel economy was substantial going from a high of 48-50 mpg to less than 40 mpg highway cruising.


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## Barry Allen (Apr 18, 2018)

CRUZE-66 said:


> 93 octane and a gallon or so of e85 added


The University of Nebraska finished up some testing of E30 in modern cars. They found that the O2 sensors, injectors, and ECU can easily accommodate E30 without illuminating a CEL. If you have any car made after about 2007 (the original EPA cutoff for E15 fuel, subsequently lowered to 2001 model years) you can probably run E30 fuel. I owned a 2009 Hyundai Accent with an 11:1 compression ratio in the engine and it ran just fine on E30 with no loss of fuel economy.

Here is an easy tool to use to calculate filling your tank with an E30 blend. You can calculate for E20 or E25 if you want to do that - the tool is flexible.





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Use the tool below to calculate an ethanol mix!


Ethanol Blend Calculator Gas tank size Gallons Liters Gasoline Ethanol Percentage E85 Ethanol Percentage Target Ethanol Mix Current Fuel Level Percentage Current Ethanol Mix Results E85 to Add Pump Gas to Add Resulting Mix




www.tuneplusinc.com


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## 17Cruzer (Apr 18, 2017)

I've used 93 octane gasoline in my Cruze since day one. The ECU was updated by the dealer when it was serviced for a leaking seal for the passenger side cv axle/transmission. Afterwards, I noticed a reduction in fuel economy and the engine felt less responsive. I do not know what was changed tuning wise via the ECU update, but I decided to fill up with 89 octane fuel. Immediately, the engine felt more responsive and with a slight gain in fuel economy!
As a side note, I no longer see the "Up to 10% ethanol" postings at the gas pumps.


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## Barry Allen (Apr 18, 2018)

17Cruzer said:


> As a side note, I no longer see the "Up to 10% ethanol" postings at the gas pumps.


It's hit and miss to find gas stations selling fuel without ethanol. My local Hy-Vee sells premium unleaded without ethanol, but the markup is huge. The local Qik-n-EZ that was closed for like 4 years after a fire opened back up and they eliminated the ethanol blend pump where I used to get E30 (had to blend it myself for my parents' Sonata when I fill it up) but I did notice they sell ethanol-free unleaded at a lot of pumps. I'll have to go back and check to see if it's 89 or 91 octane.


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## Barry Allen (Apr 18, 2018)

Here are the fuel choices at the re-opened Qik-n-EZ near me:


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