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Aug 7, 2006 | 09:05 PM

photoguy

Thread Starter

Safety Car

Joined: Jun 2006

Posts: 3,605

Likes: 2

From: Latrobe PA

Gas?

My fuel tank says high octane recommended. How much o a difference is there between 89 and 93 octane? With the price of gas is it worth it???

Aug 7, 2006 | 09:14 PM

rws.1

Race Director

Joined: Jul 2004

Posts: 16,795

Likes: 62

From: Lake Havasu City, AZ

does your car knock under full throttle and heavy load?
If not you don't need it. What octane does the manual recommend ?

Aug 7, 2006 | 09:18 PM

photoguy

Thread Starter

Safety Car

Joined: Jun 2006

Posts: 3,605

Likes: 2

From: Latrobe PA

gas

No, I have no problem with the 87 octane but I do put the 93 in about every other tank.

Aug 7, 2006 | 09:20 PM

BADDUCK

Le Mans Master

Joined: Jun 2006

Posts: 5,642

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From: One day you're a Comet...the next day you're dust... Arkansas

My 1989 says to use 91 but I can't find it around here so I mix 89 and 93 in equal parts. Kind of a PITA but the car likes it fine even in this heat. BTW fill out your profile and you will get more answers. Need to know what you have, be specific.

Aug 7, 2006 | 09:23 PM

CentralCoaster

Team Owner

Joined: May 2002

Posts: 24,337

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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed

High octane = 91+ If your choices are between 89 and 93, you should go with the 93 on your car.

Aug 7, 2006 | 09:24 PM

photoguy

Thread Starter

Safety Car

Joined: Jun 2006

Posts: 3,605

Likes: 2

From: Latrobe PA

gas

I have a 91 lt98 6 speed. The manual recommends 91 or higher.

Aug 7, 2006 | 09:32 PM

RRT vette

Le Mans Master

Joined: Feb 2006

Posts: 8,753

Likes: 9

From: Louisiana

Around here we have 87, 89, and 92 octane. My 95 doesn't mine any of them but the 86 only gets the 89+ due to knock counts. Ocassionaly I will see 93 octane at the pump.

Aug 7, 2006 | 09:40 PM

BADDUCK

Le Mans Master

Joined: Jun 2006

Posts: 5,642

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From: One day you're a Comet...the next day you're dust... Arkansas

Quote:

Originally Posted by CentralCoaster

High octane = 91+ If your choices are between 89 and 93, you should go with the 93 on your car.

Use 91 or 92 if you can find it. Anything more than your engine requires is a waste.

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Aug 8, 2006 | 12:47 AM

andon19

Instructor

Joined: May 2006

Posts: 107

Likes: 0

From: Walnut Creek California

St. Jude Donor '09

def. need 91 or above... anything else you will get knocking...

Aug 8, 2006 | 01:22 AM

#10

Paul G

Drifting

Joined: May 2001

Posts: 1,295

Likes: 2

From: Surprise Arizona

These cars have a knock sensor. If you run a lower octane than 91 you most likely will not hear anything. The sensor will pull out timing till the knock stops. Problem with that is you will loose power and efficiency. If you use premium fuel, 91 or 93 it should be okay.

Aug 8, 2006 | 01:41 AM

#11

ol school

Pro

Joined: May 2006

Posts: 536

Likes: 0

From: Humble Texas

I tried less octane gas it seemed to run okay,but I got better milage
out of the higher octane gas.. Its only a couple of dollars differance in pricing.Best to go Better.

Aug 8, 2006 | 07:44 AM

#12

Aquaman92

Le Mans Master

Joined: Aug 2004

Posts: 6,479

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From: Ponte Vedra

I use 93 octane premium at the cheapest place I can buy it (usally Murphys Mart or Sams club)

Aug 8, 2006 | 09:17 AM

#13

SJW

Le Mans Master

Joined: May 2005

Posts: 7,310

Likes: 2,231

From: Central Maryland

Quote:

Originally Posted by ol school

I tried less octane gas it seemed to run okay,but I got better milage
out of the higher octane gas.. Its only a couple of dollars differance in pricing.Best to go Better.

Fill with 91 if you can find it. Use higher octane if 91 is unavailable, or as Badduck suggested, mix 89 and 93 in equal parts to get the 91 octane you need.

As Paul G said, the ECM will retard the timing to prevent detonation if the knock sensors detect any trace of knock. This will save your engine from detonation-related damage, but will have detrimental effects upon the performance. It's not worth it. Let the engine run with the spark advance curve it was designed to use -- this requires the recommended fuel. Your engine will be happy, and so will you.

Be well,

SJW