: 106 octane in L37



mattbruz
11-15-10, 11:32 AM
What would that do to an l37 engine? Would in harm the engine at all? or would it benefit the engine due to the higher octane from premium?

Submariner409
11-15-10, 02:16 PM
What would that do to an l37 engine? Would in harm the engine at all? or would it benefit the engine due to the higher octane from premium?

Wouldn't do anything - higher octane ratings merely mean that the fuel burns slower so the engine can take advantage of slightly increased ignition timing - BUT the existing engine controls cannot move timing far enough to take that advantage, and the 4.6 Northstar doesn't require the timing advance of a longer stroke engine anyway.

mattbruz
01-29-11, 11:07 AM
In the midst of pulling codes, I went through the PCM data of the octane rating and it gave me 90. Is this normal? I have been using fuel additives for awhile. Like 104 octane boost and stp octane boost.

ThumperPup
01-29-11, 03:32 PM
not sure abou tthe GM Northstar's

but i know in my Mark VIII i woudl run 93 in it constantly always nevr lower sometimes 94 from sunoco
every ones in a whyll it would start to run ruff for some reason id run the engine down to about the last half gallon id go get a 5 gallon drump of 104 unleaded drop it in there and it would smooth out perfect
i guess it might do something to just run it threw keep it clean if you run it threw ones a year perhaps but not reeally sure

Submariner409
01-29-11, 05:08 PM
In the midst of pulling codes, I went through the PCM data of the octane rating and it gave me 90. Is this normal? I have been using fuel additives for awhile. Like 104 octane boost and stp octane boost. You have thrown away a lot of gasoline $$$ in the process..............

There is absolutely NO reason to run so-called "octane boosters". If you read the fine print it will say something like "Can raise octane by X points". Points - as in 87 octane to 87.2 octane. Snake oil at its finest hype.

You wanna "raise octane" ??? Go the local liquor store and buy a fifth of 190 proof grain alcohol (ethanol !) and dump it into a tank fillup. Ethanol is an octane booster because it slows down the rate of combustion and cools the combustion process.

Post #2

mattbruz
01-29-11, 09:07 PM
U probably already know this but I have a 20 gallon tank. Would the fifth cover the whole 20?

Submariner409
01-29-11, 10:37 PM
U probably already know this but I have a 20 gallon tank. Would the fifth cover the whole 20?

Put this all in context - you're searching for some sort of "performance increase". My post was tongue-in-cheek advice that you might as well forget it from a standpoint of pouring magic potions into your gas tank ! Think about it: Your tank holds 20 gallons of gasoline. 1/5 gallon is 1/100 of the total volume........so you would be far, far better off by running a decent brand of 89 or 93 octane gasoline - Chevron, Shell, or Texaco. Google "top tier gasoline" to find out why.

Ranger
01-30-11, 01:16 AM
There is absolutely NO reason to run so-called "octane boosters". If you read the fine print it will say something like "Can raise octane by X points". Points - as in 87 octane to 87.2 octane. Snake oil at its finest hype.
:yup:

zonie77
01-30-11, 01:27 AM
As Sub said, high octane gas burns slower...and it's resistant to "knocking" so it can support higher compression. If the engine was designed to need 100 + octane you would get a benefit. Since the N* is designed to run on lower octane you will get little or no benefit. The timing will advance more, but I think the computers are fairly limited in max advance.

A long, long, long time ago, when dyno tuning ruled the earth, HAHA , I would have to manually adjust timing for different octane gas, but it still wasn't a huge difference.

mattbruz
01-30-11, 11:43 AM
Well I am now just seeing the light in all of this.*sigh* I have been using bp but I'll look it up as you said. I know engine is amazing for it being stock. I was just looking for better mpg in the city. I currently get 13.6-17 mpg city. 17 mpg being very conservative on the pedal. And 13.6 dogging the engine for performance.

Submariner409
01-30-11, 11:49 AM
If you're getting 13.6 - 17 in the city that's right in the ballpark with every other Northstar owner. ETC/DTS/STS should see ~24/25 on the Interstate. ELC/Deville/DHS/SLS, about 26/27. The difference between model types is the 3.71 final drive compared to the 3.11.

97EldoCoupe
01-30-11, 02:17 PM
Or like my one '97, have the L47 Aurora 4.0 motor coupled to the 3.11:1 final drive in an Eldorado. Nobody can beat my highway mileage :)

mattbruz
01-30-11, 02:33 PM
3.71; I guess I shouldn't be too worried about it.