Switching to Premium gasoline

[Nessism1]

I never understood why anyone would want to run 87 octane in a car designed to run best on 93.

Where I live, So. Calif, you can't buy 93, other that at specialty stations which are rare and far apart.

And what cars are "designed to run best on 93?"

Regarding my "turbo" car, I run it on 87, just as Honda recommends. I've tried 91, the highest commonly available, and noticed no difference in how the engine ran, nor in mpg. 3 mpg more with premium fuel? Not in my car.

 

[Patman]

Where I live, So. Calif, you can't buy 93, other that at specialty stations which are rare and far apart.

And what cars are "designed to run best on 93?

The C7 Corvette Z06 and ZR1 for sure, both of them being supercharged and 93 is absolutely necessary. I was just reading about an owner of a Z06 who says that if he runs 91 octane and makes a few full throttle pulls it will actually go into limp home mode. It’s just pulling way too much timing out in order to compensate for the lower octane.

Even my non supercharged C7 doesn’t like 91, I can hear detonation at part throttle in the 1500 to 2000 rpm range.

 

[Nessism1]

The C7 Corvette Z06 and ZR1 for sure, both of them being supercharged and 93 is absolutely necessary. I was just reading about an owner of a Z06 who says that if he runs 91 octane and makes a few full throttle pulls it will actually go into limp home mode. It’s just pulling way too much timing out in order to compensate for the lower octane.

Even my non supercharged C7 doesn’t like 91, I can hear detonation at part throttle in the 1500 to 2000 rpm range.

Does GM sell those vehicles in California? Is there a special tune? If not, what to do?

 

[Patman]

Does GM sell those vehicles in California? Is there a special tune? If not, what to do?

They do sell them there and the tune is the same. A lot of guys will buy 100 octane race fuel and mix it with 91 to get the desired 93+
Others may never have a problem if they don’t go full throttle at all.

 

[Jetronic]

11.5:1 CR on the 15e4e engine in the MG ( GM 1.5 ecotec turbo-gdi). Didn't notice any difference between RON95 and RON98. But I guess both could be considered premium? 95 RON minimum they say...

 

[tiger862]

Uncalculated and not scientific. People read manual and see 87 so they run 87. I generally run 2 tanks regular and then 2 tanks midgrade and see if it's worth it. Caravan stated 87 and higher octane wouldn't make a difference except in cost. No difference so 87 was it. I just purchased a 2020 frontier and manual states "at least 87". Engine blew before I could run testing.
2024 Frontier loaner was according to fuel efficiency meter was 20.2 regular mixed driving then I switched to midgrade. On second tank now and fuel mileage shows 23.8 mpg. Same driving condition. Truck is smoother as well.
Now when I get my truck back I will run same test and go from there. I don't worry about fuel mileage as much as the way it shifts and accelerate, then mileage. Now with new Frontier it's a break even point since I get more miles per tank so that would be a wash.

 

[CleverUserName]

I’ve rented Chevy malibus recently with the 1.5 TGDI. I tried filling up with 91 because it was sluggish on 87. It had better throttle response and I beat the EPA highway fuel economy of 37 MPGs with 91 under less than ideal driving conditions.

If I owned a TGDI I would experiment with higher octane as it may run better in addition to lower FD.

 

[John105]

Turbo = premium. I don't care who you are.

What if my name is Mick Jagger? Still no 87 in my boosted ride?!

 

[John105]

I’m no longer driving my LS430 to work as my wife is using it. Premium is expensive on our side of the river.

Had to do it. Got 91 for $3.579. 93 was 6 cents more. Regular 3.059. To illustrate, Costco 93 is $3.179 where I work. My rationale is CA only had 91 from what I’ve heard.

 

[y_p_w]

Where I live, So. Calif, you can't buy 93, other that at specialty stations which are rare and far apart.

Basically only available if it's blending in 100 AKI street legal race fuel. I've heard of some people referring to it as "Smurf gas" because it's usually dyed blue. Not sure what meets California RFG requirements though.

And premium is 91 when it was typically 92 up to maybe the late 90s.

 

[ChrisD46]

In hot humid summer conditions (SE USA) I found premium grade gas made the engine perform better where as regular gas grade ran fine in the cooler months .

 

[wemay]

No difference whatsoever in my Malibu 1.5T. It runs great on Marathon 87.

 

[Jetronic]

In hot humid summer conditions (SE USA) I found premium grade gas made the engine perform better where as regular gas grade ran fine in the cooler months .

It makes sense that the hotter it is, the higher the octane number requirement is. In the end, the temperature in the combustion chamber after compression drives the need, and that will be higher when the air going in is hotter.

 

[John105]

No difference whatsoever in my Malibu 1.5T. It runs great on Marathon 87.

Doesn't the owner's manual recommend 87? If so, there will be as you say, no difference whatsoever. I get we cannot break the chains that bind, so many equate octane with "goodness" and "how much they care about their engines." This type of thinking permeates almost every aspect of life. If I spend $1400 on ice skates, I will have a distinct advantage over someone who only spent $600. You will. That is if you have the skills to utilize the marginal benefit of the design that went into the more expensive skates.

Just as if the engineers designed an engine for 91+, it will benefit from the higher octane. If they designed it for 87, the 91 or 93 is simply burned out the tailpipe with nary any benefit.

 

[CharBaby]

I've never really noticed enough difference in premium fuel over regular fuel.
When gas was .10c-.20c more a gallon for premium gas over regular gas, I would try it for several tankfuls to see if there was any significant benefit for me, my car, my driving style & climate. But now with premium fuel(in my area) being over $1/gallon more, that's $15-$20 more per tankful, every tankful and I'm not spending that every week for no benefit that I can measure. If I had something that required premium, it'd be a different story.

When premium gas was maybe 7% more money per tankful, I might get 6%-8% better fuel economy and maybe(only maybe) better throttle response! So there was a close to break even factor.
Now, premium is 35% more money and there is no way that I am going to achieve 35% better fuel economy nor anywhere close to that in performance/throttle response.

This is my take on it.
If I want a fast car, I'll buy a fast car. If I want my fast car to go faster, I'll buy a faster car.
If I want my car to get better fuel economy, I'll buy an economical car.
If I want my car to handle better, I'm not going to change my tires, shocks, sway bars etc., I'm going to buy a car that can handle.

 

[k1xv]

Some are willing to run 87 in a car where 91-93 is recommended, in order to save money.

But are unwilling to cheap out on motor oil when Mobil 1 is recommended. Did a car ever "wear out" from using the non specified brand of oil, but instead using a less pricey oil of similar viscosity?

Driving a Corvette with well over 1 hp per cubic inch, gasoline seems to be a poor area to go below owners manual recommendation. Sort of like putting S speed rated tires on a car that came fitted with V speed rating, because you do not drive over 110 mph.

 

[Patman]

Some are willing to run 87 in a car where 91-93 is recommended, in order to save money.

But are unwilling to cheap out on motor oil when Mobil 1 is recommended. Did a car ever "wear out" from using the non specified brand of oil, but instead using a less pricey oil of similar viscosity?

Driving a Corvette with well over 1 hp per cubic inch, gasoline seems to be a poor area to go below owners manual recommendation. Sort of like putting S speed rated tires on a car that came fitted with V speed rating, because you do not drive over 110 mph.

I may have mentioned this before, even in this thread but there is a guy on the Corvette Forum who has been putting 87 octane in his 2017 Corvette, despite the fact that the owners manual says that 93 is HIGHLY RECOMMENDED. He even lives in Texas so I can’t imagine how he hasn’t blown up his engine yet with all of those 100+ degree days.

 

[TiGeo]

I have multiple posts here to back regular vs. premium with data logs. If not it's most likely all just...

 

[TiGeo]

Here's a few logs showing knock sensors for our VW Atlas. One on 87 one on 93. Variables controlled to level they can be. Winter blend fuel so worst case. The Atlas rated for 87 AKI min sees some benefit power-wise running 93 based on these data. Unless you see this it's not doing a thing to run premium. I have seen no mpg difference that would be measurable or could ever offset the nearly dollar per gallon cost difference. We run 87...there is no feel difference I can discern. Cars run a bit down on power when its hot out due to high intake air temps.

Post in thread 'Why 93 Octane in a GDI engine if it isn’t called for?' https://bobistheoilguy.com/forums/t...ine-if-it-isnt-called-for.379664/post-6803055

 

[odie]

Use Top Tier 90 > 94 for the '25 SOULs' since buying new .