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2018 CTS Premium Luxury 3.6L
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Discussion Starter · #1 ·
It says in the manual use 87 or higher. I'm surprised that the 3.6L will run fine with regular octane, but will there be a performance or noticeable mpg increase with premium fuel?

This has probably been asked to death, so I apologize in advance. I just wasn't expecting to see that in the manual. Was expecting high octane premium only.
 

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SRX,ATS,CTS(2), CT6
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199 Posts
87 octane is all you need for knock prevention. Higher octane might even make a tiny reduction in mpg.

However.... direct injection engines have greater propensity to create valve deposits due to lack of fuel washing the intake valve. Higher QUALITY fuel (not necessarily higher octane) 'might' do some good in keeping combustion chamber deposits down due to more/better additives. But, even 94 octane super duper with tons of detergent etc still wont be passing over the intake valve, so it can't really help that problem. Your owners manual and your dealer service advisor will tell you "gm recommends top tier fuel" meaning something with a decent ration of detergent added to the basic gasoline. This top tier designation used to be limited to stuff like shell and bp. Now im seeing the label on pumps at lower priced sunoco and murphy etc.

I suggest anything over 87 is wasting your money. If you suspect deposits are forming, nothing you put in the tank is likely to help. You need something you introduce via the intake airstream like a top cylinder cleaner. Unless you have good evidence of an actual problem, run 87 and enjoy life.



Sent from my SM-G960U using Tapatalk
 

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2016 AWD 2.0T LUXE, 2016 C7 TBDE vert, 2012 911S Cab., 2003 Avey Z66
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714 Posts
Anything over the 87 for you is a waste in my experience...now my turbo is another story. They recommend 93 and that's what I've used since I ran out the tank of 87 the dealer put in it. Even so, I rarely get into boost and "could" use 87 without issue but I just do the 93.
 

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2018 CTS Premium Luxury 3.6L
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10 Posts
Discussion Starter · #4 ·
87 octane is all you need for knock prevention. Higher octane might even make a tiny reduction in mpg.

However.... direct injection engines have greater propensity to create valve deposits due to lack of fuel washing the intake valve. Higher QUALITY fuel (not necessarily higher octane) 'might' do some good in keeping combustion chamber deposits down due to more/better additives. But, even 94 octane super duper with tons of detergent etc still wont be passing over the intake valve, so it can't really help that problem. Your owners manual and your dealer service advisor will tell you "gm recommends top tier fuel" meaning something with a decent ration of detergent added to the basic gasoline. This top tier designation used to be limited to stuff like shell and bp. Now im seeing the label on pumps at lower priced sunoco and murphy etc.

I suggest anything over 87 is wasting your money. If you suspect deposits are forming, nothing you put in the tank is likely to help. You need something you introduce via the intake airstream like a top cylinder cleaner. Unless you have good evidence of an actual problem, run 87 and enjoy life.



Sent from my SM-G960U using Tapatalk
I'll do some research on "top tier" fuels in my area. The manual mentions that too.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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73,911 Posts
TopTier gasolines - ALL grades of a certified brand contain the necessary additives.


All our cars use efficient knock sensors - if you tow, track the car, or do mountain driving use a higher octane fuel for a while. Remember - if you have an 18 gallon tank 1/2 full of 87 and fill it with 93 then what you're burning is 90 octane . . . . . little or no difference whatsoever.
 

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2018 CTS Premium Luxury 3.6L
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Discussion Starter · #6 ·
TopTier gasolines - ALL grades of a certified brand contain the necessary additives.


All our cars use efficient knock sensors - if you tow, track the car, or do mountain driving use a higher octane fuel for a while. Remember - if you have an 18 gallon tank 1/2 full of 87 and fill it with 93 then what you're burning is 90 octane . . . . . little or no difference whatsoever.
Yeah looks like most stations in my area are top tier. I'm partial to Shell myself but it's good to know.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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I use Valero, Shell, Sunoco, BP, and EXXON/Mobil as available. Here in 21666 Thursdays are "Thirsty Thursday" and Shell is a nickel off. My Sunoco card gives me a nickel off every day and the local station across from the Shell competes with them so I get a dime off on Thursdays. :cool:
 

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2000 Deville DHS
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1,262 Posts
I use Valero, Shell, Sunoco, BP, and EXXON/Mobil as available. Here in 21666 Thursdays are "Thirsty Thursday" and Shell is a nickel off. My Sunoco card gives me a nickel off every day and the local station across from the Shell competes with them so I get a dime off on Thursdays. :cool:
And when it’s all said and done you’re saving .40-.80 cents everytime you pump gas… That’s not even enough to buy a cup of coffee.

Is it really worth the time to try and bargain hunt for such minimal savings? Wouldn’t it be worth it to just go to the gas station that you prefer?

There’s also the fact that we decided to drive Cadillacs, not Toyota Prius’ lol.
 

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2000 Deville DHS
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1,262 Posts
I did some math the last time I was at the gas station. According to my cars Trip cpu I had used 9.5 gallons of gas since my last fill, so that’s how much gas I needed.

The most expensive option: 91 octane/Credit or Debit price $4.59 for 9.5 gallons =



Cash price for 91 octane / $4.44 for 9.5 gallons =



Cheapest option: Cash price regular 87 octane / $4.14 for 9.5 gallons =




So here in California, I’d save $4 dollars filling up at half tank of gas if I were to pay cash and choose regular 87 octane vs. most expensive option 91 and pay with card.

Estimated savings would be around $6 dollars per full tank since nobody realistically allows their tank to get bone dry before filling up.

FYI: I filled up with 91 octane and paid cash.
 

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2018 CTS 3.6 RWD, going between FL and MI I average 34-36 mpg on 87 octane, around town its between 23-25 mpg.

COG
 

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2014 XTS Luxury & 2021 CT5 Premium Luxury
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661 Posts
Old thread, but: I have a 2010 Acadia with a 3.6. About 6-7 years ago, it would continue cranking, after engine had started. Service manager recommend using mid-grade gas from a Top Tier station. I have not had an issue since. The vehicle has 135K, running on the same plugs. But, it is on my things to do list.

P.S.
Vehicle still gets estimated MPG: 17/24.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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And when it’s all said and done you’re saving .40-.80 cents everytime you pump gas… That’s not even enough to buy a cup of coffee.
Is it really worth the time to try and bargain hunt for such minimal savings? Wouldn’t it be worth it to just go to the gas station that you prefer?
We have no allegiance to any particular brand of gasolines. All equally satisfactory.

I usually fill when the tank is down to 1/4 - so nowadays it's about 13 gallons once a month for the Explorer, once every 5 months for the STS, 3 gallons a month for yard equipment. Each of the mentioned gas stations is close together, less than 2.5 miles from home, and on my normally travelled shopping routes so there's no bargain hunting - I use the info in GasBuddy so it's "know before you go".

Use 21666 as the zip code lookup, click the zoom box upper right, zoom in to Kent Island - we live north of Rt.50 about 2 miles. Piece of cake -

 

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2000 Deville DHS
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1,262 Posts
We have no allegiance to any particular brand of gasolines. All equally satisfactory.
Cool, but while brand preference is of higher importance to some people, I was more so talking about a gas station that someone might prefer based on things like it being close to home or maybe next to the freeway they take to work, or maybe they like the hot chocolate or sandwiches they have at that gas station, could be a pretty girl that works behind the counter that they enjoy flirting with. Lol.

Brand loyalty/preference is definitely a thing for some though, I’m not saying it’s not. For me personally it’s less about a brand and more about uniformity, meaning I feel better knowing the same kind of gas always goes into my car instead of one week this kind and next week that kind.
 

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2014 XTS Luxury & 2021 CT5 Premium Luxury
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As for brands, I like Chevron. But, it is no long in the area. So, I look for an Exxon, Shell or Mobil. My thought is a clean burning gas. I tried BP and got a sluggish acceleration. Since there are more Exxon stations than Shell in the area, I find myself at Exxon stations. But having a choice between Shell or Exxon, I typically will pull into a Shell station. There may not be much of a difference. But, one Shell station that I frequent mid-grade is Ethanol free, which seems like a cleaner burning blend to me.
 

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2018 CTS Premium Luxury 3.6L
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Discussion Starter · #15 ·
I'm still thinking of using some Shell V-Power in my 2018 CTS. Not necessary as I'm not suspecting any issues at all with deposits but I do like the idea of the extra detergents, and maybe I'm a sucker for their promotion material lol.
 

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I always use Shell, in Canada V-Power (top of the line) is $1.64/litre right now, ouch. So the past two months I've dropped down to 87 octane ($1.39) at Shell and aside from saving $10 per tank I see zero difference in performance. So I'll be sticking with 87 until the price comes down, as if that will ever happen.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Gasoline additives and their proprietary names are carefully chosen for the most hype effect. One of the additives in the TopTier fuels is/was/may be a variant of the Chevron TECHRON series that is marketed/licensed under several names. BP's "Invigorate" comes to mind. BUT any gasoline marketer (brand name) is free to use any of their own additives in addition - as long as the total package meets or exceeds the "TopTier" licensing requirements.

If Shell wants to put "Nitro" in their 93 and "NotNitro" in their 87/89 fuels that's OK. But it all has the minimum required TopTier package.

Post #5, the link. As I've posted before, it's interesting to watch the Eagle, Shell, independent, Eastern Petroleum, other carrier tankers pull into the depot at Dorsey Road near Baltimore, dump the necessary ethanol and additives from a few tanks, load a dozen different brands of gasoline from the same spout, and head out. Then watch 3 different carriers fill the underground tanks at the local Sunoco station.


Google "petrochemical pipeline separation pig" to learn how that 750,000 gallons of plain old gasoline gets to the depots, immediately followed by 1,000,000 gallons of diesel.

p.s. - some gasolines are different colors - that's all done at the loading depot too.
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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Our engines are Direct Injection (DI). Fuel does not pass over the valves to clean them. It won't matter what fuel you use.
 
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