question about gasoline use

[SuLLiVaN88]

on my 90 gts it says premium fuel recommended is this only for this motor or is that a suggested use on all 4a's or only for the ge's?

[eage8]

Originally Posted by SuLLiVaN88

on my 90 gts it says premium fuel recommended is this only for this motor or is that a suggested use on all 4a's or only for the ge's?

it's actually only for the smallport 4ages (90-91) (and also 20Vs and gzes...)

all the other 4As are fine with 87.

[SuLLiVaN88]

Originally Posted by eage8

it's actually only for the smallport 4ages (90-91) (and also 20Vs and gzes...)

all the other 4As are fine with 87.

so why the difference between the small and big port motors?

i put 87 in it the first time because i didnt see the sticker and being oblivious i figured it would use just reg 87 but now i put 91 in it lol

[eage8]

Originally Posted by SuLLiVaN88

so why the difference between the small and big port motors?

i put 87 in it the first time because i didnt see the sticker and being oblivious i figured it would use just reg 87 but now i put 91 in it lol

small ports have much higher compression (10.3:1 vs. 9.4:1)

[SuLLiVaN88]

Originally Posted by eage8

small ports have much higher compression (10.3:1 vs. 9.4:1)

this is true that thought didnt even cross my mind lol

[SuperRA]

I have a smallport and I run 87 all the time with no problems. Only if I want to eek out the extra few RPM and HP will I put in premium.

[Evo_lucian]

small port 4agze, and 20v will run fine on 87, though 91 is highly recommended.

[REN69]

depends on the gasoline though... I've noticed little to no difference running 89 to 91, I did notice some difference running 87 to 91 though so I stick to mid and high grade.

[Kiwi-Corolla]

While we're on the topic of octane ratings, what's the highest octane you guys get in the states?

Here in New Zealand, 91 octane is the lowest and 98 octane is the highest.

[PrizmGSi]

Originally Posted by Kiwi-Corolla

While we're on the topic of octane ratings, what's the highest octane you guys get in the states?

Here in New Zealand, 91 octane is the lowest and 98 octane is the highest.

I know it doesn't take any brains to copy & paste but I couldn't come up with as clear an answer as Wiki...

In Europe 98-octane gasoline is common and in Japan even 100-octane is readily available at the pumps, but this octane nomenclature is misleading to Americans as foreign octane ratings are derived entirely differently from our own... So, like every other measurement system it seems that everyone else uses a different scale than we do, but unlike most other instances where we have had the good sense to create different units of measure in this case we all use the same name...
Japan and Europe use a system called RON or Research Octane Number to determine the octane rating of their gasoline, while stateside we use a system called AKI or Anti-Knock Index to determine gasoline's octane rating... Interestingly, to further complicate things it would seem that our own AKI system is actually derived from the average of the RON system and another more complicated system referred to as MON or Motor Octane Number... So, to recap our methodologies for measuring gasoline's octane rating are different, but share some common elements...
So, with the commonality of RON in mind a good rule of thumb is as follows, multiply the foreign RON Octane rating by 0.95 and you will have the US AKI equivalent.

( RON Octane Rating x 0.95 = AKI Octane Rating )
98 RON Octane x 0.95 = 93.1 AKI Octane (US measure)
100 RON Octane x 0.95 = 95 AKI Octane (US measure)

So, as you can see the 93 or 94 octane fuel we are all paying an arm and a leg for is actually quite comparable to the higher octane fuels found in Europe and Japan. The people whom have to worry about low octane rating are our friends out west in places like California that are subjected to substandard 91 octane.
91 AKI Octane (US measure) = 95.5 RON Octane

[Kiwi-Corolla]

^ Cheers, that makes a lot of sense. So your 87 octane is basically the equivalent of our 91 octane. Good to know