Do you use regular or premium? LTG engine.

[saab93driver]

Everyone here doesn't have a 2018, mine is a 2014 and many others here also have the early LTG.

This is the 2018+ Buick Regal Sportback and TourX forum, so that is generally the target audience of people responding. There are other forums for the other models and years.

 

[BoostedRegal2.0]

A lack of data points surely can't allow us to know the full picture. The fact still stands that GM says 87 octane fuel is safe for our 18+ LTGs.

According to the poll, most people in this post are using premium, so obviously they don't have much faith in what GM says or thinks. You can run whatever octane fuel you want in your car and I won't try to change your mind.

I've always run 93 octane and with 85,000 miles on my tuned early troublesome LTG engine the pistons haven't been damaged. So evidently 93 octane fuel is a safe choice.

 

[hoys]

According to the poll, most people in this post are using premium, so obviously they don't have much faith in what GM says or thinks. You can run whatever octane fuel you want in your car and I won't try to change your mind.

I've always run 93 octane and with 85,000 miles on my tuned early troublesome LTG engine the pistons haven't been damaged. So evidently 93 octane fuel is a safe choice.

I run premium and regular depending on my expected driving conditions. A poll of 28 people on an enthusiast group certainly isn't a good way to collect an overall statistic.

Certainly on a vehicle with a tune above the factory GM conditions a higher grade fuel is more appropriate. Although it is good to note that Trifecta mentions their tune is suitable for all octane levels as well:

-Tested on all available grades of fuel (87, 89, 91, 92, and 93 octane).

2018--2020 Buick Regal - 2.0L Turbo - Advantage

 

[BoostedRegal2.0]

Trifecta won't pay for your motor if it blows up so they can say whatever they want. Then you are at the mercy of the knock sensors, but I've already said that it's not a good idea to rely on them since knock has to happen for the ECM to pull boost/timing. If you want to get the Trifecta tune and run 87 octane I won't hold it against you!

 

[hoys]

Trifecta won't pay for your motor if it blows up so they can say whatever they want. Then you are at the mercy of the knock sensors, but I've already said that it's not a good idea to rely on them since knock has to happen for the ECM to pull boost/timing. If you want to get the Trifecta tune and run 87 octane I won't hold it against you!

Most certainly they don't provide any financial support. Their statement does provide knowledgeable insight into the capabilities of the stock system to detect knock at different octane levels. I firmly believe they know more than you and I combined about the system so I'll defer to the experts. In other wide range knock systems on modern ECUs, they can detect wider ranges of engine noises than just 15 years ago. Previous to wide range knock detection systems the sensor would only respond in certain harmonic ranges that it was built to respond to. With newer sensors and ECU strategies maps are able to be built with much more prediction of knock events based on overall engine noise. Knock isn't an absolute binary value of "yes knock" or "no knock". It's the flame front igniting too quickly inside the chamber. This can happen at more than one point of piston position in its stroke and more than one specific cylinder load. Again I'm not an expert on the 2018+ control strategy, but I know that knock detection and ECU capability has come a long way. Previously held truths are far obsolete.

 

[Buschb]

GM recommends 93....I run 93

Hell, it's only 3/4 more $$ a tank.
If 10 bucks a month is going to mess up your budget, don't buy a new car!!

 

[D2R]

According to the poll, most people in this post are using premium, so obviously they don't have much faith in what GM says or thinks. You can run whatever octane fuel you want in your car and I won't try to change your mind.

I've always run 93 octane and with 85,000 miles on my tuned early troublesome LTG engine the pistons haven't been damaged. So evidently 93 octane fuel is a safe choice.

I cannot speak for other fellows here, so only talking about my own use case.
It has nothing to do with if I have faith in what GM says or thinks.
I look at it this way. The difference of cost to fill up between a tank of premium vs a tank of regular in my area is under $5.
How much is it going to hurt me to lose this lovely wagon if anything goes wrong? Can I get something equivalent to replace her?
What did I pay the vehicle for? 250 HP and 295 lb-ft of torque or something less?
As an engineer, I don't like to take those gambles or risks.

 

[BoostedRegal2.0]

Most certainly they don't provide any financial support. Their statement does provide knowledgeable insight into the capabilities of the stock system to detect knock at different octane levels. I firmly believe they know more than you and I combined about the system so I'll defer to the experts. In other wide range knock systems on modern ECUs, they can detect wider ranges of engine noises than just 15 years ago. Previous to wide range knock detection systems the sensor would only respond in certain harmonic ranges that it was built to respond to. With newer sensors and ECU strategies maps are able to be built with much more prediction of knock events based on overall engine noise. Knock isn't an absolute binary value of "yes knock" or "no knock". It's the flame front igniting too quickly inside the chamber. This can happen at more than one point of piston position in its stroke and more than one specific cylinder load. Again I'm not an expert on the 2018+ control strategy, but I know that knock detection and ECU capability has come a long way. Previously held truths are far obsolete.

If you knew how many motors blew up from a ZZP tune it would make your jaw drop. They are supposed to be experts too, so that's why I'm not going by what Trifecta says and rely on the knock sensors to protect my motor.

 

[BoostedRegal2.0]

I cannot speak for other fellows here, so only talking about my own use case.
It has nothing to do with if I have faith in what GM says or thinks.
I look at it this way. The difference of cost to fill up between a tank of premium vs a tank of regular in my area is under $5.
How much is it going to hurt me to lose this lovely wagon if anything goes wrong? Can I get something equivalent to replace her?
What did I pay the vehicle for? 250 HP and 295 lb-ft of torque or something less?
As an engineer, I don't like to take those gambles or risks.

I don't think much of GM at all. At this moment my wife's Regal is at the dealer getting one or both rear wheel bearings replaced for the third time. The rear wheel bearings they replaced all lasted about a year. THAT IS TOTALLY REDICULOUS!!!!!!

 

[D2R]

I don't think much of GM at all. At this moment my wife's Regal is at the dealer getting one or both rear wheel bearings replaced for the third time. The rear wheel bearings they replaced all lasted about a year. THAT IS TOTALLY REDICULOUS!!!!!!

You know...if it is being replaced the third time, it could potentially be something else causing this.
Replacing a failed part does not mean it corrects the root cause. That is like putting a bandage.
Did the dealer actually find out what is causing the failure or did they only care to charge for warranty repairs?

 

[BoostedRegal2.0]

Come to find out the dealer didn't check for a TSB on the Regal and I found there's one to install dust covers to protect the wheels bearings from water and dirt. So I gave them the TSB number and they looked it up and made a note of it. So maybe the new bearings will last way more than a year this time!

 

[Zeroboostbuick]

Why when it’s hot?? Are you referring to high and low volatility?

Hot air will cause more pre-detonation. Even tho our cars have an intercooler, the hot outside air can only cool so much through the intercooler.

Pre-Detonation ( Knock ) is caused by heat.

Octane Rating = Anti-Knock Index (In North America)

Octane Rating in Europe uses a different method, thus European 95 Octane is like 91'ish in North America.

Pre-Detonation is detected by the Knock Sensors. When they sense pre-detonation, they RETARD the Ignition Timing accordingly to compensate. That's why some call it Knock Retard.

Up to 10 Degrees of Knock Retard is still safe, but if you get a spike of 15+ degrees of KR, that could damage the engine instantly.

Colder air is denser and lowers the cylinders temperature, thus helping to keep the pre-detonation at bay.

Other things that cause heat, in turn cause pre-detonation. Like higher compression ratio, turbos and blowers all create more heat than otherwise. So the antidote is higher octane, aka gasoline that is harder to pre-ignite by hot spots in the cylinders.

 

[BoostedRegal2.0]

I agree with most of that except colder air expands more than hot air, so even when it's cold outside the combustion temp can rise and cause knock. For that reason I run 93 all year long, not just when it's hot outside.

 

[Zeroboostbuick]

I agree with most of that except colder air expands more than hot air, so even when it's cold outside the combustion temp can rise and cause knock. For that reason I run 93 all year long, not just when it's hot outside.

I scan with HPTuners so I easily see how much Knock Retard is happening on a hot day and on a cold day and everything in between.

I too use mostly 91 with the occasional 94 octane.

If someone doesn't have a scanner of some sort that can read Knock Retard, then I don't recommend them using 87 except in sub freezing temps.

 

[BoostedRegal2.0]

I wonder if I can scan for KR with my Trifecta tune and laptop. I know it will do data logging so I'll have to look into that.

 

[Zeroboostbuick]

I bet you can, because KR is a very important tuning parameter.

 

[BoostedRegal2.0]

Right but I can't modify the Trifecta tune so that's why I'll have to check it out.

 

[autocomman]

AAA did a huge study on this a few years back. Long story short of you out in what the manual recommends. Not what it says you 'can use' but what it says you should use. Open the fuel door on the 2.0t car it says use premium, so that's what you should use. It's not worth the power loss is possible engine damage from saving a few $ on a tank full. The flip side, if it recommends regular, your wasting money and not gaining any performance using premium.

 

[Hunter Mike]

The fuel door says “recommends”. Problem solved, 87 it is.

 

[landsharkmz3]

As I suspected in this thread, there is lots of opinions, hand waiving, misquoting the manual, misquoting other people, and even the obligatory "as an engineer" statements. I could make a long involved post on the topic, but I simply am not going to put that kind of effort into it as people will just try to shout rebuttals based on god knows what.

Here are the cliff notes.
The sensors and control system can detect if you are running 87 vs 93 by operating characteristics. There are calibration tables to operate in both conditions. The tables when running higher octane a slightly more aggressive and will give a small bump in power. This small power increase is what is used to publish the power ratings, and GM wants to claim the best number they can claim. THAT is the reason GM lists 93 as "highly recommended for best performance and fuel economy", as they can benefit from ratings at no cost to them. GM does not require 93. 93 is not even offered at most stations in my area. GM requires a minimum of 87. The engine is designed, validated and warranted to run this fuel if the owner chooses.

Which fuel is right for you?

• Do you want every possible ft-lb for your lead foot? Pick 93+
• Do you want peace of mind on GM recommendation and don't care about cost? Pick 93+
• Do you drive not WOT everywhere, in normal conditions, and want to save from unnecessary costs? Pick the best BTU/$, and here's how...
  • Its more about ethanol than octane.
  • E0 has ~125 kBTU/gal. E100 is ~76 kBTU/gal
  • Attached is a picture of a pump near my house a couple months ago.
  • These prices and content equal out to 87E10= $0.22/kBTU ; 88E15= $0.20/kBTU ; 91E0= $0.28/kBTU
  • This makes 88E15 the best value, with 91E0 being 29% more expensive for equivalent energy.

...and just for fun, I will throw in my own obligatory "as an engineer" plug... and no, I will not be arguing with anyone over this.