Purpose of 89 Octane?

[The Critic]

Around here, pumps have dispensers for 87, 89 and 91 octane fuels.

I have seen cars specify either 87 or 91, never 89. So what's the purpose of 89?

 

[VK56VD]

Good question. I'd like to hear the answer as well.

 

[tomcat27]

in my humble opinion, I think its to squeeze some extra profit outa people who want something better than regular, but wont pay for premium.

It appears to me that 89 is simply a blend of regular and premium - I could be wrong - but on one of the pumps I used both counters incremented when pumping midgrade.

 

[The Critic]

Originally Posted By: tomcat27
in my humble opinion, I think its to squeeze some extra profit outa people who want something better than regular, but wont pay for premium.

It appears to me that 89 is simply a blend of regular and premium - I could be wrong - but on one of the pumps I used both counters incremented when pumping midgrade.

89 is blended at pump. I'm curious what the ratio of 87 to 91 is though, in order to make an 89 blend.

 

[Quattro Pete]

Originally Posted By: The Critic

89 is blended at pump. I'm curious what the ratio of 87 to 91 is though, in order to make an 89 blend.

Probably close to 50/50.

As for the purpose of 89, I know a lot of small engines (lawn equipment) recommends mid grade fuel.

 

[tomcat27]

I run premium in 2 cycle engines... a lesson I learned after the rings stuck in my 85 hp outboard years ago -

 

[The Critic]

Originally Posted By: tomcat27
I run premium in 2 cycle engines... a lesson I learned after the rings stuck in my 85 hp outboard years ago -

How does 91 octane prevent ring stick?

 

[justinf89]

89 is recommended in most marine applications. I know my generator and mains require 89

 

[genynnc]

My 03 Ram w/ Hemi specifies 89 octane in the manual. (Although I use 87 with no reported probelms).

 

[hate2work]

Originally Posted By: tomcat27
I run premium in 2 cycle engines... a lesson I learned after the rings stuck in my 85 hp outboard years ago -


I doubt the octane of your gas had anything to do with your rings sticking.

 

[hardcore302]

I use 89. Just because. I'm serious.

 

[Summerwind]

I run 89 in My Merc GMQ, however it has a custom tune for it..Allows for a higher advance on the timming without detonation I would guess. RE: Old outboards, I remember years ago, my Dad would only run "High-Test" "White gasoline" (1960's here) in our Merc outboards...they ran like "banshees" on it

 

[Stu_Rock]

I had 1994 and 1995 GM cars with the L82 3100 engine. They called for 89 octane.

I did some experimenting with the '95 by watching the knock count on my scan tool. Some stations' 87 would work just fine, while others would knock a little.

Then I put a 180°F thermostat in, and basically all brands of 87 worked fine. Citgo in Wis. and QuikStop in Calif. were still bad.

 

[Craig in Canada]

My current vehicle recommends 91 or 92 (I forget which) with a minimum of 89 (not 87). If I wanted to fuel it with the cheapest/minimum I would run 89.

Perhaps there are other cars out there with similar specs.

 

[purelux]

I've heard that sometimes as a engine gets older and higher in mileage and deposits bumping up a bit to 89 from 87 can help if you're experencing knock. Though were it to be true a good cleaning should allow you to go back to 87. As for using 87 instead of 89 prob not as much as going from 91-93 to 87 but still probably dropping performance and mpg. No reported problems is a rather broad term. You kicked out the cash for a hemi but can't spend $2-3 more on gas? If you do a comparison 1 fill up to another remenber it often takes a few tanks for the computer to reset/relearn to compensate.

 

[stenerson]

I use 89 cause my manual says to use it for optimum performance.

 

[Spyder7]

I use 89. Manual says "87 or higher." 89 is 3 cents a liter more; gas prices are currently $1.05 for 87, so from dry tank to full the difference is $54 instead of $52.50. The small difference in cost doesn't bother me. Car seems to like 89 better and I think I get slightly better mileage on it too (back when I kept track, my best tanks were always the 89 fills).

-Spyder

 

[Durango]

If gas goes any higher in my area then maybe I may have to buy gas outta the region/area of buy lower for my 08 Impala SS which requires 91 octane gas.

You don't want to know how much the Shell gas station is asking for it's gas in all grades!!!

Durango

 

[rslifkin]

With the HEMIs 89 is recommended, but the knock sensor will cut it back to run on 87, so 89 isn't required.

My Jeep requires 91 minimum, and I put 93 in it (we have 87-89-93 here). When the plenum gasket went, I knew pretty quickly, as just the little bit of extra oil vapor being sucked into the intake was enough to make it ping lightly around 2/3 throttle, even on 93. The timing is pushed pretty hard on this thing.

 

[mechtech2]

Some cars are indeed rated for 89, or maybe 87 or 89.
But in any event, if there is pinging/spark knock with 87 that goes away with the mid grade, it is good to use it.