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Discussion Starter #1
i am currently using 87 octane because i am cheap. the ride is fine with no ping's, knock's or stutter. my question is would my gas milage be higher with higher octane fuel? if i was to get better mileage i would spring for the higher priced gas and it would offset the price by better milage. anyone know?
 

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2018 XT5
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637 Posts
No you will not get better mileage using higher octane gas. It has been said many times in the papers etc. that it is unwise to burn higher octane gas than is required. It makes the engine run hotter, leaves unburned deposits and is a waste of money. The person who tells you that he gets better mileage than he did on regular doesn't need premimun gas, just a better quality brand of regular.
 

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Discussion Starter #4
manual says 91 recommended but not required. they claim you will get more power from higher octane gas, which i guess makes sense. i don't notice any less power when using 87 octane.
 

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2006 STS V8 Lux, 2011 Escalade EXT Prem
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I've tested 87 vs. 93, no change in gas mileage. I run 87. Cannot tell the difference in the STS.
 

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2006 STS V8 AWD, '95 Ford Ranger
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If you drive the car hard enough to encounter spark rap with 87 octane the ECU is going to retard the ignition timing and your milage will drop. I found with my STS that over the same 750 mile drive that intermediate grade is good for an additional 2MPG for the way I drive. If you never get on the car hard enough to cause detonation you'll never see a difference.
 

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'06 Northstar STS 1SG, PHP, ACC/HUD '06 Redline CTS-V, FG2
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I, too, run my '06 Northstar on 87 octane regular. It seems to be thriving. The only place it seems to make a measurable and repeatable difference is at the drag strip where premium reduces my et by about 0.2 second (to 14.5 from 14.7 running regular).

Binky Bear's buddy is probably right: retarded timing (and maybe altered valve timing) increase fuel consumption. But my driving is not consistent enough to yield a measurable and repeatable mileage difference.
 

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Discussion Starter #10
its actually closer to $6 more per tank. multiply that by 50 times per year and your looking at around $300. not a deal breaker but if i could save it why not?
 

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2008 CTS
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its actually closer to $6 more per tank. multiply that by 50 times per year and your looking at around $300. not a deal breaker but if i could save it why not?
I also burn regular in my 05 STS no performance problems and mileage is 18.4 at the moment around town and I can get as much as 25 straight highway driving and I'm talking 80MPH. I have a 48 month lease and that's 1200 bucks for the life of the car. Looks better in my pocket than big oil's.
 

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06 STS-1SG-ACC/HUD-Volant CAI-Corsa Exh-Mesh Grill-ClearBra
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its actually closer to $6 more per tank.
Relative to the state where you purchase as a caveat.

In SoCal the price differential is generally .20 between 87 and 91 (93 not readily avail).

That's $3.00 on a 15gal fill...

Of course with several threads on this subject already. What is really obvious is it has less to do with actual price and more on subjectivity.

The debate refuses to die :bandwagon:
 

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Sedan de Ville, CTS
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Certain years require prem. (Early models.)

You can google reviews on cars. They will typically provide needed octane.
 

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2006 STS V8 AWD, '95 Ford Ranger
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interesting, i've never seen this in any vehicle i've owned.
I drive hard enough that when using regular, the engine encounters spark rap or pinging and the PCM retards ignition timing which reduces engine power and milage slightly. Intermediate grade is sufficient to prevent this detonation for me so the ignition timng stays advanced. The engine is designed to protect itself from damage from detonation with the use of regular gas but with reduced performance. The level of effects of this protection feature are determined by your particular driving style. If you drive in a very reserved manner you'll never see the difference. If you like to hear the wonderful sound of that very intense engine winding out through the gears it'll be very evident.
 

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10 CTS-V, 13 ESCALADE, 06 C6, YAM R1
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574 Posts
I drive hard enough that when using regular, the engine encounters spark rap or pinging and the PCM retards ignition timing which reduces engine power and milage slightly. Intermediate grade is sufficient to prevent this detonation for me so the ignition timng stays advanced. The engine is designed to protect itself from damage from detonation with the use of regular gas but with reduced performance. The level of effects of this protection feature are determined by your particular driving style. If you drive in a very reserved manner you'll never see the difference. If you like to hear the wonderful sound of that very intense engine winding out through the gears it'll be very evident.

oh i definitely understand how the pcm works, just never heard of anyone gaining more than tenths of a mile by switching octanes. i tune the high octane table to eliminate knock, and then copy it to the low octane table, so there is no chance of the engine "learning" in this manner.

good for you...2mpg is incredible:worship:
 

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2006 STS V8 AWD, '95 Ford Ranger
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oh i definitely understand how the pcm works, just never heard of anyone gaining more than tenths of a mile by switching octanes. i tune the high octane table to eliminate knock, and then copy it to the low octane table, so there is no chance of the engine "learning" in this manner.

good for you...2mpg is incredible:worship:
Over the same 360 mile route in the same weather conditions, milage went from 19.7MPG to 21.7MPG calculated from gallons pumped and miles covered. It surprised me too. I had always been a sceptic as well. I'll maybe hook up my OBDII scanner and do some data logging to see what's going on.
 

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2006 STS V8 AWD, '95 Ford Ranger
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i tune the high octane table to eliminate knock, and then copy it to the low octane table, so there is no chance of the engine "learning" in this manner.

good for you...2mpg is incredible:worship:
What software and what fixture are you using to tune the STS PCM?
 

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2001 Cadillac Eldorado ETC
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912 Posts
Dkozloski; during the last phases of the cold war my National Guard unit got its wartime mission to defend in place, with M-16s, in the Aleutian Islands against those mean, nasty Ruskies who would be invading America from the west. The island had a runway and a Navy weather unit, and lost of cold rocks. Us Ohio Infantry boys thought that freezing to death defending the great state of Alaska was – well, don’t bother me with the re-enlistment speech. 50 below zero is not our cup of tea. However, in the briefings and training, in order to try to get us interested, the higher headquarters showed us a picture of a bear, almost like the one you are using as a self portrait, except this on had a salmon in his/her mouth. They said that was the sexiest thing on the island. I hope that doesn’t represent the whole state of Alaska, too. :usflag:
 
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