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Author Topic: Public service announcement about octane requirement.  (Read 2467 times)

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Offline jeremysdad

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Public service announcement about octane requirement.
« on: April 02, 2014, 06:36:14 PM »
I finally (it took a while to find the perfect search query) found something that I find definitive regarding the fact that my 72's Owner's Manual requires 91 octane (Premium today). Apparently, the gas is basically the same, but they changed the formula that determined octane.

Found here: http://forum.studebakerdriversclub.com/archive/index.php?t-44301.html

Quoted response:

"Keep this in mind when thinking about octane levels in gasoline. Prior to 1972 in the US the posted pump octane was the Research Octane Number (RON), this number is still used in Australia and Europe. The current (Post 1972) octane posed on the gasoline pumps in the AKI (Anti-knock Index) or some times shown as (R+M/2) which means it is the average of the old RON value and the Motor Octane Number (MON).

As a rule of thumb the difference is about 4 octane numbers (exact calculations would be dependent on additives, ethanol content and other variables) so for the common grades now sold in the US I will list new and old methods.

New: AKI (R+M/2) vs. Old: RON

87 ____ 91
89 ____ 93
91 ____ 95
93 ____ 97"

Apparently, that's also why thousands of BMW owners are still scratching their heads and running race gas or octane boosters. :) lol

Just wanted to pass this along, now that I found it. I ran midgrade (89) and/or premium (93 here), but recently have been running regular due to budget. It was relieving to know I wasn't hurting it. :)

Regarding the source, I figure if it's good enough for a Stude, it's good enough for a Pinto. ;)

Offline rramjet

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Re: Public service announcement about octane requirement.
« Reply #1 on: April 02, 2014, 06:52:46 PM »
Great info. I knew there had been a change back in the dark ages but couldn't remember which way it went. I did assume that with 8.5:1 compression the thing should run fine on 87 and it does. The only knock I hear is one of the rods when I go over 45 mph. :-\

Offline Wittsend

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Re: Public service announcement about octane requirement.
« Reply #2 on: April 02, 2014, 07:07:26 PM »
Interesting that you found the information at the "Studebaker Drivers Club."  When I'm not hanging out here, I'm over there.



Offline jeremysdad

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Re: Public service announcement about octane requirement.
« Reply #3 on: April 02, 2014, 07:08:47 PM »
I think it was the leaded/unleaded thing that had me so confused.

I hope you get that fixed. :) I can't tell from a 3/4 rear photo...what year is that/what motor are you running?

Offline jeremysdad

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Re: Public service announcement about octane requirement.
« Reply #4 on: April 02, 2014, 07:11:53 PM »
Is that an Avanti? :) lol

(Ed: I know what a Studebaker is, but couldn't identify one from an Edsel at a car show, except that the Edsel has that egg-sucker grill). :) lol

Idk...took me two years to find it, but that's where it was. :)

Offline Wittsend

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Re: Public service announcement about octane requirement.
« Reply #5 on: April 02, 2014, 07:25:42 PM »
Avanti?  Nope.  A '64 Daytona. Studebaker dropped the "Lark" terminology after '63.  A bit of an odd pedigree.  Studebaker stopped USA production at the end of '64. This however is a Canadian built car where they built the last remaining Studebakers until they closed in '66. In '65-'66 Studebaker used GM 283's.  Mine had one of those engines (referred to as McKinnon's because that is the GM subsidiary that built them).

So, logic says I should have a USA built '64, but it was made in Canada. It is a year too early for the GM 283, but it seems I have had a transplant.  Later I installed an '85 Corvette 350 (switched to carburation) and a 700R4 trans.

To keep the post on track..., it runs fine on 87 octane.  ;D

Offline amc49

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Re: Public service announcement about octane requirement.
« Reply #6 on: April 03, 2014, 10:25:17 PM »
Sort of a moot point with all the variance they do with ethanol content. Here they can have up to 20% real world measurement even though the legal number is 10%. More ethanol pings less even though it makes for crappier mileage.

Offline Wittsend

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Re: Public service announcement about octane requirement.
« Reply #7 on: April 03, 2014, 11:44:59 PM »
Maybe they should make a "Breathalyzer" for the gas pump to see if it is "over the limit."  LOL

Offline 74 PintoWagon

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Re: Public service announcement about octane requirement.
« Reply #8 on: April 04, 2014, 07:35:02 AM »
Maybe they should make a "Breathalyzer" for the gas pump to see if it is "over the limit."  LOL
Don't say that too loud you'll give em ideas, lol..
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