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Discussion Starter · #1 ·
This is getting very confusing. After reading this article https://www.digitaltrends.com/cars/why-new-cars-recommend-premium-fuel/

Yeah, G.M. say 87 octane is fine but I heard here and a few other places that 91 is better. Is this just placebo like this article says or is there TRUE and PROVEN benefits in using 91 octane in my 2018 Hatch?

I need more than someone telling me..."sure it's better". I need concrete evidence since my car is still brand new and I want to make sure it runs top at all time but I don't want to pay more for something that really isn't better in the end and just makes me feel better. Thanks for anyone having hard evidence that 91 octane is better, if not, I'll continue putting regular unleaded.
 

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Try 2 tanks and see what you think.

In my car, the LE2 has much better low-end response, acceleration is smoother and less jerky, MPG is slightly better, and I have had zero instances on 93 where the car suddenly pulls all power after I hear a knock from the engine.

The new 1.4T and 1.5T engines have had instances of people blowing pistons apart from LSPI. Most of those cars have been run on lower octane with lower-quality oils.
 

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The new 1.4T and 1.5T engines have had instances of people blowing pistons apart from LSPI. Most of those cars have been run on lower octane with lower-quality oils.
Do we really know that already, any links to those findings? We do know certain model year CRUZE operate fine on Regular Fuel with ambient heat being the major factor.
 

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I'm in the try two tanks of mid-grade (89) and then two tanks of premium (91 or higher). GM did a lot to make these engines safe to run on 87 octane, but that safety comes at the cost of overall drivability.
 

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I don't notice any difference between 85 and 89. And will probably go back to using 85. After I've tried ethanol free first.

Now if you want to talk oil. Then we can talk BIG difference.
 

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GM says to use 91 in my 13 cruze. I use 89 due to the high cost of 93 in my area. Around me at the stations it 87, 89, then 92 or 93. 92 or 93 is 60-70 cents more per gallon than 87 and 30-40 cents more than 89. the stations with 92-93 costs the same so in the summer I use 93 since it doesn't cost any more than 92, oh and I get about 5 more mpg with 93 vs 89.
Your results may vary.
 

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For me, I tend to look at the situation logically. I spent a lot of time researching this one.

Octane is a measure of a fuel's resistance to pre-ignition (AKA Pinging, knocking, exploding too early) It's caused when the air/fuel in the cylinder reaches a condition where it spontaneously combusts. When you put a volatile substance under pressure, it increases temperature too, and it may choose to ignite all on it's own if it has enough of either heat or pressure. 87 Octane will run just fine at sea level on your average naturally aspirated car. You can even sort of get away with running 85 octane out in the midwest where the air is really thin and the atmospheric pressure is lower, though I personally wouldn't even use 85 in my lawn mower.

Turbocharged vehicles have more of both heat and pressure. The turbo is connected to the exhaust so it transfers heat to the intake air, and then it compresses it which adds more heat. It goes through an intercooler to try to remove some heat before going into the engine but the air going in is still much higher pressure than non-turbo cars. Then you mix in the gas and you shove it in a hot piston which compresses it even more, and you have to hope it doesn't explode before the spark plug can get to it.

The Cruze does indeed fall into the gray area of new cars where 91+ is RECOMMENDED but it is not REQUIRED The car has sensors in it to monitor knocking and it will retard engine timing to fight the pre-detonation if you choose to run 87. This is where you start to see the decrease in performance. Now this is debatable. If you're the type of person who won't notice a bad wheel bearing, you probably won't notice the difference in power. If you're like me, and you live between 4,500 RPM and 6,500 RPM pushing full boost all the time then the car is going to constantly be pulling timing getting worse fuel mileage and less power while also destroying itself. If you cruise on the interstate 95% of the time, then you might just be wasting money.

Final thoughts: I run 93 octane fuel from top tier gas stations in both my vehicles that recommend them because I hate the thought of the long term harm 87 may cause. Personally I can feel a difference in the Cruze, I notice the decrease in fuel economy, and I can watch on my ultra-gauge the change in engine timing by about 5-15 degrees of advance when idle and as much as 30 degrees less of timing advance under load in boost. The engine has a shuddering almost "heart palpitation" feeling right before it pulls a lot of timing, which is what I believe to be knocking when I run 87.

Do some research, try them for yourself (it takes a few tanks for the computer to completely adjust to the fuel), do the fuel calculations, and draw your own conclusions.
 

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The Cruze does indeed fall into the gray area of new cars where 91+ is RECOMMENDED but it is not REQUIRED
Where did you get that from? I'm looking in my 2013 owners manual on page 9-46 under Recommended Fuel. Use regular unleaded gasoline with a posted octane rating of 87 or higher. If heavy knocking is heard when using gasoline rated at 87 octane or higher, the engine needs service.

Nowhere does it say 91+ is recommended.
 

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I don't notice any difference between 85 and 89. And will probably go back to using 85. After I've tried ethanol free first.

Now if you want to talk oil. Then we can talk BIG difference.
Minimum required is 87...do not run 85 in a turbo motor

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He must be at a high elevation where the thinner air allows lower octane gas to be used. Of course the engine puts out less power.
 

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Show me a photo of that please.
Look for KRD on the glove box sticker. If your car has the KRD code this means the engine is designed to run on 91 octane and the reason it can run on 87 is the result of a sophisticated knock sensor system and smart software to detune the engine.
 

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I don't notice any difference between 85 and 89. And will probably go back to using 85. After I've tried ethanol free first.

Now if you want to talk oil. Then we can talk BIG difference.
Don't run 85 in these engines. 85 works in naturally aspirated engines because the external air pressure is lower due to altitude, lowering combustion chamber pressures. Lower pressures are less likely to have fuel predetonation. Turbo charged engines compensate for the external air pressure drop to keep the effective altitude for the car at sea level.
 

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He must be at a high elevation where the thinner air allows lower octane gas to be used. Of course the engine puts out less power.
He's in the Rocky Mountains (I checked the IP address). We also have 85 octane in Denver - the Cruze was the first car I've driven that absolutely hated 85 octane. I won't put it in my Volt either even though it has a NA gas engine for on-board electric generation.
 

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He must be at a high elevation where the thinner air allows lower octane gas to be used. Of course the engine puts out less power.
Doesn't matter. 87 is the minimum required by GM. It is not tuned to run on anything lower than that, and may risk blowing apart a piston. It's in the manual.
 

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He must be at a high elevation where the thinner air allows lower octane gas to be used. Of course the engine puts out less power.

But if it's turbocharged and computerized, it'll try to make full power on bad gas.
 

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Discussion Starter · #20 ·
Look for KRD on the glove box sticker. If your car has the KRD code this means the engine is designed to run on 91 octane and the reason it can run on 87 is the result of a sophisticated knock sensor system and smart software to detune the engine.
I would like to look at this sticker but there's none in the glove box. I checked in the hatch, under the panel that covers the spare tire also nothing there. Where is it located on a 2018?
 
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