91 vs 95 octane?

**Adriaan** · 11th December 2011, 08:22

Does anyone have a preference and why ? Are there any pro's or con's to either ?

Thanks

**Latte** · 11th December 2011, 08:30

Use the lowest octane you're bike is rated for. All my bikes are 95 (but they run fine on 98). My cars are all 91.

The lower the octane the more chance of detonation. But the faster flame front should produce more power if it's tuned for it.

**flyingcr250** · 11th December 2011, 09:21

I heard european/american RON95 was the same as our 98

**Jay GTI** · 11th December 2011, 10:14

We measure RON, whereas the Americans measure PON, which is an average of RON and MON (RON being the higher value).

**Sable** · 11th December 2011, 10:40

Also DON and JON, don't forget

**thecharmed01** · 11th December 2011, 11:07

Depends on the vehicle.
When it comes to cars, I'll always run the highest octane I can get as Japanese imports (which is what I drive most often) are all tuned and built to run on higher octane fuel than anyone supplies here.
If you do have a japper, then you are better to run as close to 98 as you can get.

I'm not sure if the same applies to NZ built cars though as I would hope they are tuned for NZ fuel, which is not overly good.

I don't think there are any fuel companies providing a true 98 octane fuel here. They might call it 98 but it isn't. BP have the closest with their high octane fuel, which is not at all stations and we try to only use the BP high octane in the bikes.
I would never run 91 in my bike if I didn't absolutely have to as higher octane fuel delivers more power. And it's all about the power isn't it

**wickle** · 11th December 2011, 11:13

[QUOTE=Latte;1130212328]Use the lowest octane you're bike is rated for. All my bikes are 95 (but they run fine on 98). Cars are all 91.

incorrect : some euorpean vechilles are 95 or better

**Fast Eddie** · 11th December 2011, 11:55

Originally Posted by Latte

Use the lowest octane you're bike is rated for. All my bikes are 95 (but they run fine on 98). Cars are all 91.

The lower the octane the more chance of detonation. But the faster flame front should produce more power if it's tuned for it.

Cars are not all 91..

**barty5** · 11th December 2011, 11:57

just use 95 or 98 forget about using 91

**Jay GTI** · 11th December 2011, 13:11

Originally Posted by sable

also don and jon, don't forget

don jon son?

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**onearmedbandit** · 11th December 2011, 13:29

91 is crap. Wouldn't even run it in my lawn mower.

**bsasuper** · 11th December 2011, 13:30

Ron makes the fuel sound good, take 3 points off to get the right figure

**Latte** · 11th December 2011, 13:49

[QUOTE=wickle;1130212383]

Originally Posted by Latte

Use the lowest octane you're bike is rated for. All my bikes are 95 (but they run fine on 98). Cars are all 91.

incorrect : some euorpean vechilles are 95 or better

Sorry, meant My cars.

**Jay GTI** · 11th December 2011, 13:55

Originally Posted by thecharmed01

Depends on the vehicle.
When it comes to cars, I'll always run the highest octane I can get as Japanese imports (which is what I drive most often) are all tuned and built to run on higher octane fuel than anyone supplies here.
If you do have a japper, then you are better to run as close to 98 as you can get.

I'm not sure if the same applies to NZ built cars though as I would hope they are tuned for NZ fuel, which is not overly good.

Common myth, they have the same octane fuels we do, the only difference is they can get 100RON as well. But the idea they are all running around with tanks of 100+RON super fuel isn't true.

Originally Posted by thecharmed01

I don't think there are any fuel companies providing a true 98 octane fuel here. They might call it 98 but it isn't. BP have the closest with their high octane fuel, which is not at all stations and we try to only use the BP high octane in the bikes.

From what I understand no-one gets a true 98RON fuel, worldwide it's made by taking a lower RON fuel and mixing it with octane-boosting additives. Some people believe these additives leach out within 2 weeks of production, so that by the time you put it in your car it's not 98RON anyway.

Originally Posted by thecharmed01

I would never run 91 in my bike if I didn't absolutely have to as higher octane fuel delivers more power. And it's all about the power isn't it

Another myth sorry, higher octane doesn't equal more power. The octane rating is simply a method of measuring the resistance to detonation. From that, the higher the octane, the higher the compression ratio you can use, or the further the ignition advance you can set. On something relatively dumb, like your average carb-fed dirt bike, using high octane fuels will gain you absolutely no power at all over a low octane fuel, unless you map or change your ignition to suit (it's generally static). However on most modern cars the ECU is intelligent enough to be able to actively monitor detonation and advance or retard the ignition to suit the RON of the fuel you're using, so theoretically you'd make more power on 98RON fuel over 95RON or what ever. But even then, in terms of actual, real-world power increases, it's so minimal you won't notice.