regular gas
Safety Car
Joined: Sep 2006
Posts: 4,075
Likes: 6
From: Wilmington NC
And that does'nt take into consideration that you will get poorer gas mileage with the lower octane gas.
Safety Car
Joined: Jun 2004
Posts: 3,563
Likes: 2
From: Dallas Tx
Or that ECM knock sensing can only adjust timing and fuel to reduce spark knock. How about preignition? That is when the A/F mixture self ignites even before the spark plug fires. On a car that is preigniting, like a 10.9 to CR motor running on 87, you can pull all the timing you want the the knock will still be occuring. Now you've got the car running on the retarded ignition map, less than ideal combustion occuring = more carbon build up = more spark knock.
When I was a tech, I saw it all the time with the blue hairs running Kroger 87 in a 50 grand Caddy with a Northstar that recommends premium. After about a year the comb chambers would be so carboned up the pistons would be hitting the heads on cold starts. Top engine clean it, tell them to run premium. They'd bitch and moan, OK see you again in 6 months, and they'd be back. After about the 3rd injector and top engine cleaning, some would finally quit running grocery store 87 and switch to a name brand premium.
Took me 3 years and 3 top engine cleanings on my dad's DeVille to get him to stop using his Kroger discount for gas. This is where you buy groceries, and let's go down the road a bit, this is where to by the good gas. After that, his caddies have been running perfect ever since.
When I was a tech, I saw it all the time with the blue hairs running Kroger 87 in a 50 grand Caddy with a Northstar that recommends premium. After about a year the comb chambers would be so carboned up the pistons would be hitting the heads on cold starts. Top engine clean it, tell them to run premium. They'd bitch and moan, OK see you again in 6 months, and they'd be back. After about the 3rd injector and top engine cleaning, some would finally quit running grocery store 87 and switch to a name brand premium.
Took me 3 years and 3 top engine cleanings on my dad's DeVille to get him to stop using his Kroger discount for gas. This is where you buy groceries, and let's go down the road a bit, this is where to by the good gas. After that, his caddies have been running perfect ever since.
Team Owner
Joined: Nov 2007
Posts: 45,267
Likes: 8,542
From: Rochester, NY
I would follow the words of wisdom as stated here and conclude bad idea.
Your car. Your money. Only you can decide if it feels right to you. The car will retard the performance to match the reduced octane until it can't reduce it anymore. Once that happens you will get knocking and pinging. That can damage your engine. Pay attention to what the car is telling you.
I can't imagine that they put that in the manual just for kicks.
The manual states the following:
Gasoline Octane
Use premium unleaded gasoline with a posted octane of
91 or higher for best performance. You may also use
middle grade or regular unleaded gasoline rated at 87
octane or higher, but your vehicle’s acceleration may be
slightly reduced. If the octane is less than 87, you may
get a heavy knocking noise when you drive. If this occurs,
use a gasoline rated at 87 octane or higher as soon as
possible. Otherwise, you might damage your engine.
I can't imagine that they put that in the manual just for kicks.
The manual states the following:
Gasoline Octane
Use premium unleaded gasoline with a posted octane of
91 or higher for best performance. You may also use
middle grade or regular unleaded gasoline rated at 87
octane or higher, but your vehicle’s acceleration may be
slightly reduced. If the octane is less than 87, you may
get a heavy knocking noise when you drive. If this occurs,
use a gasoline rated at 87 octane or higher as soon as
possible. Otherwise, you might damage your engine.
Team Owner
Joined: Sep 2005
Posts: 29,113
Likes: 2,194
From: Big Bend Country, TX
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15- '16-'17-‘18-‘19-'20-'21
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Team Owner
Joined: Sep 2005
Posts: 29,113
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From: Big Bend Country, TX
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15- '16-'17-‘18-‘19-'20-'21
NCM Lifetime Member
Using this logic, it is best not to do the following with our $60K sports car:
1) Never track it or do a burn out - bad for the drive train
2) Never drive it on the freeway - might get a chipped windshield or a paint chip.
3) Never park near a curb - might get curb rash
4) Never sit on the seats and fart - it might scorch the leather.
5) Etc. Etc.
1) Never track it or do a burn out - bad for the drive train
2) Never drive it on the freeway - might get a chipped windshield or a paint chip.
3) Never park near a curb - might get curb rash
4) Never sit on the seats and fart - it might scorch the leather.
5) Etc. Etc.
Burning Brakes
Joined: Nov 2007
Posts: 1,002
Likes: 0
From: Virginia Beach VA
I don't think I'd run the 87 octane... the 89, ok, that's what I'm running now.
From Click and Clack:
"Use the grade of gas you need and nothing higher.
Does your owner's manual say "Premium Unleaded Only"? No? Then don't ever use premium fuel. There. We just saved you 40 cents a gallon... or $8 on a 20-gallon fill up. If your engine is designed to run on regular gas, there's absolutely no benefit to putting in "high test." It pollutes more, it costs more, and doesn't give you any benefit in performance or fuel system cleanliness.
Now, what if your car DOES call for minimum 91 octane? Well, next time you buy a car, dumkoff, check what kind of fuel it requires first. We've always said that once you buy the car, you're stuck. You've got to use 91, because your high compression engine will ping if you don't. But now, most cars have "knock sensors," that retard the timing via the engine management computer (effectively lowering the compression) to protect the engine, in the event that you happen to get some bad gas, or have an emergency and can only get regular grade fuel. So we got to thinking, what would be wrong with using the knock sensor all the time? What if you put regular gas in the car all the time and let the knock sensor do its job and retard the timing? You'd have a little less power, but that extra 8 bucks a fill up might be more important to you than power right now. It would be to us.
It's a controversial theory, we admit it. But that's never bothered us before. And we can't think of any long-term effects of driving with the knock sensor retarding the timing. So our position (for the time being) is... use regular. Who cares? Now, if there are any actual automotive engineers in the audience who have worked on knock sensors, who want to tell us why we have our heads up our keisters, feel free to write to us. And if we're convinced that we're wrong, we'll happily change our recommendation."
From Click and Clack:
"Use the grade of gas you need and nothing higher.
Does your owner's manual say "Premium Unleaded Only"? No? Then don't ever use premium fuel. There. We just saved you 40 cents a gallon... or $8 on a 20-gallon fill up. If your engine is designed to run on regular gas, there's absolutely no benefit to putting in "high test." It pollutes more, it costs more, and doesn't give you any benefit in performance or fuel system cleanliness.
Now, what if your car DOES call for minimum 91 octane? Well, next time you buy a car, dumkoff, check what kind of fuel it requires first. We've always said that once you buy the car, you're stuck. You've got to use 91, because your high compression engine will ping if you don't. But now, most cars have "knock sensors," that retard the timing via the engine management computer (effectively lowering the compression) to protect the engine, in the event that you happen to get some bad gas, or have an emergency and can only get regular grade fuel. So we got to thinking, what would be wrong with using the knock sensor all the time? What if you put regular gas in the car all the time and let the knock sensor do its job and retard the timing? You'd have a little less power, but that extra 8 bucks a fill up might be more important to you than power right now. It would be to us.
It's a controversial theory, we admit it. But that's never bothered us before. And we can't think of any long-term effects of driving with the knock sensor retarding the timing. So our position (for the time being) is... use regular. Who cares? Now, if there are any actual automotive engineers in the audience who have worked on knock sensors, who want to tell us why we have our heads up our keisters, feel free to write to us. And if we're convinced that we're wrong, we'll happily change our recommendation."
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Team Owner
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From: Big Bend Country, TX
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15- '16-'17-‘18-‘19-'20-'21
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Team Owner
Joined: Mar 2008
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From: Southern Utah
Team Owner
Joined: Sep 2005
Posts: 29,113
Likes: 2,194
From: Big Bend Country, TX
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15- '16-'17-‘18-‘19-'20-'21
NCM Lifetime Member
Team Owner
Joined: Sep 2005
Posts: 29,113
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From: Big Bend Country, TX
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15- '16-'17-‘18-‘19-'20-'21
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Team Owner
Joined: Mar 2008
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From: Southern Utah
The only time the timing is being retarded is when the knock sensors are hearing knock, which is usually at lower RPM and lots of throttle. When cruising on the highway at 5% throttle going 80MPH, the sensors will not cause spark retard, therefore no worse gas mileage.
Team Owner
Joined: Sep 2005
Posts: 29,113
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From: Big Bend Country, TX
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15- '16-'17-‘18-‘19-'20-'21
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Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
It works like this. Most Brands of premium contain more detergents and cleaners
than in the regulars 87. Some of the cheaper one just barely meet the EPA minimum requirements. Octane is not the only difference between premium and regular. (In most cases) We ran a Lumina APV 230,00 mile on Amoco 93 and never touched the TBI injectors with any cleaners or additives. It ran as good as new. I'll stick with 93. MAYBE I would consider 87 for my lawn mower... Wait ..... On second thought ...NOT!
Race Director
Joined: Jun 2005
Posts: 10,909
Likes: 2,701
From: Phila Suburbs 2023 C8 & 2013 650ix
Gasoline Octane
Use premium unleaded gasoline with a posted octane of
91 or higher for best performance. You may also use
middle grade or regular unleaded gasoline rated at 87
octane or higher, but your vehicle’s acceleration may be
slightly reduced. If the octane is less than 87, you may
get a heavy knocking noise when you drive. If this occurs,
use a gasoline rated at 87 octane or higher as soon as
possible. Otherwise, you might damage your engine.
Would somebody explain where this manufacturer's recommendation says that Regular 87 will harm your engine? IT DOES NOT! The only effect is that "acceleration may be slightly reduced." I think GM engineers know more about this engine and it's operational characteristics than this group of worry warts.
Use premium unleaded gasoline with a posted octane of
91 or higher for best performance. You may also use
middle grade or regular unleaded gasoline rated at 87
octane or higher, but your vehicle’s acceleration may be
slightly reduced. If the octane is less than 87, you may
get a heavy knocking noise when you drive. If this occurs,
use a gasoline rated at 87 octane or higher as soon as
possible. Otherwise, you might damage your engine.
Would somebody explain where this manufacturer's recommendation says that Regular 87 will harm your engine? IT DOES NOT! The only effect is that "acceleration may be slightly reduced." I think GM engineers know more about this engine and it's operational characteristics than this group of worry warts.
Le Mans Master
Joined: Feb 2008
Posts: 5,636
Likes: 1,185
From: Lake Worth Beach, Florida
In general won't hurt the car, won't gum the injectors, but if you drive with a lot of acceleration or in mountainous areas you could cause extreme pre-ignition which would cause damage.
The difference between the lower octane and the higher octane is only the octane rating, not the additives.
Higher octane burns slower than lower octane which allows a more advanced ignition spark which allows the engine to burn cooler.
If you compute the difference in cost, you will probably find that you will be saving only a couple of hundred dollars over the course of a year.
The difference between the lower octane and the higher octane is only the octane rating, not the additives.
Higher octane burns slower than lower octane which allows a more advanced ignition spark which allows the engine to burn cooler.
If you compute the difference in cost, you will probably find that you will be saving only a couple of hundred dollars over the course of a year.