100 Octane

[avrflr]

I have a little inside knowledge (I work for BP, not pumping gas). I agree that you won't get any benefit on a stock 250 from higher octane fuel. Some people wouldn't even notice the difference between 91 and 95. If you raised the compression of your motor it might make more power, but you then might run into problems with detonation, so then you would need higher octane fuel. I would say at least 90% of people think that if you put avgas in a street car/bike it will instantly turn into a rocketship. And don't get me started on confusing avgas with jetfuel. Very frustrating for a fuel nerd. If you are having problems on pump fuel with a stock bike, a tune might help.

[Motu]

Octane boosters work,if you need them - but not Wynns,I've used that crap and it did nothing.You need 104,or 108 octane booster - get them from Pioneer or Segiden Truck and Auto.But my old Falcon needed it,the old 2 valve high compression motor rattled like diesel - why do you need an octane booster???

[Sutage]

i disagree
98 feels smoother and runs a hell of a lot better and has quicker acceleration i find
plus its like 12c more in my 11litre tank its like.. 1 dollar, the small notice is worth 1 dollar to me
91 can leave a build up of shit in ur tank too

[SPman]

Some bikes do prefer a high octane rating. I've noticed on mine that it has a slight pause when snapping the throttle open on 95 but doesn't do it on 98. Seem to get better milage on 98 too.

I noticed it liked 98...91 was OK ...hated 95

[avrflr]

i disagree
98 feels smoother and runs a hell of a lot better and has quicker acceleration i find
plus its like 12c more in my 11litre tank its like.. 1 dollar, the small notice is worth 1 dollar to me
91 can leave a build up of shit in ur tank too

Hmm, interesting. 98 doesn't have much additive in it because it's refined specifically to be a 98 octane fuel. I've heard that engines running on premium tend to have less carbon build up in them, but I've never heard of 91 leaving "shit in ur tank". Shit can end up in the fuel at the gas station for all sorts of reasons....

[sAsLEX]

Very frustrating for a fuel nerd.

ok maybe you can explain. 98/95/91 and all this is just a octane right!? all using the same basic fuel with shit added in to raise the octane rating without increasing the amount of octance in there, so getting to my question: is 98/Ultimate/other generic high perfomance petrol any better than the rest of the shit the big 4 bring in to this country!?

[avrflr]

ok maybe you can explain. 98/95/91 and all this is just a octane right!? all using the same basic fuel with shit added in to raise the octane rating without increasing the amount of octance in there, so getting to my question: is 98/Ultimate/other generic high perfomance petrol any better than the rest of the shit the big 4 bring in to this country!?

The fuel at most gas stations (91 and now 95) gets refined at marsden point. Various additives are injected just before it gets loaded into the tanker. The additives have various purposes like detergents to dissolve the shit in your fuel system and octane enhancers. The mobil premium fuel for example has an octane of 97.3 or something.

98 is different, it is refined in western australia and shipped to tauranga. It still has additives injected before it goes in the tanker, though.

[sAsLEX]

thought it must be, used to be best to get challange gas as that was shipped from overseas rather than marsden, we are finally getting slightly better deisel *sp* in some places is this shipped or refined here? I ask this as I read a comparisn of the black pump fuel a while back and we were on par with Nigeria for Sulphur levels etc

[Toast]

I noticed it liked 98...91 was OK ...hated 95

I think a lot of people find this. I do. Carb'd bikes especially seem to hate the extra additives in 95/96.

I always use 98 when it's available (BP only, Mobil stuff is just 96 with even more shit in it). My 'Blade seems to run a couple of degrees cooler in equivalent riding conditions, compared to 91, too.

[avrflr]

Sorry to go OT but yeah, our diesel is refined here and the reason we have high sulphur levels is money. Marsden pt wasn't originally set up with low sulphur diesel in mind so will require major investment to fix, which is why they will drag their feet all the way.

[FlyingDutchMan]

Sorry to go OT but yeah, our diesel is refined here and the reason we have high sulphur levels is money. Marsden pt wasn't originally set up with low sulphur diesel in mind so will require major investment to fix, which is why they will drag their feet all the way.

They've completed the upgrade of Marsden point about a month ago - all diesel here is now low sulphur. Read this:

http://www.consumer.org.nz/newsitem....on%20the%20way
Its also the reason for 95 octane at the pump now instead of 96.

[Hitcher]

So what's being postulated is a premise that there is a bunch of additives that can be added to your fuel at the bowser that improve the performance of that fuel in your engine, over and above all of the stuff that the oil companies already add?

With the exception of the tetra-ethyl lead substitute that comes in the orange syringes for use with older cars, I would say "What a load of crap!"

At best Wynns (and other proprietary) additives are harmless. Caveat emptor.

[Motu]

As the adds say - they contain ''JET'' fuel.....true,they are mainly kerosine.But I know for sure that 104 and 108 octane boosters work,my Falcon engine was built before non lead fuel,and the only way to stop it rattling was 100 octane or 104 and 108 boosters,I tried the ''service station'' boosters like Wynns and STP,but they never worked.When the BP ultimate came out I ran it on that exclusively,and it ran fine.It's only old school cast iron head 2 valve combustion chambers running 60s high compression that need high octane,most standard engines built after the late 70s will run on anything.

[scumdog]

Put 98 in my 'lorry', it certainly pinked a whole lot less than with 96, ran a little better around town too.

Went TOO well outside Dangerous Drop-in Dwelling but that's another story...

[Fooman]

...CNG!

CNG has an octane rating of 120ish! If it's high octane, it must be good! Actually the only problem with CNG (other than tank range), is that the engine also had to run using petrol, which meant that the engine was optimised for neither!

There are a number of issues with petrol/octane/leaded/unleaded/additives:

As mentioned, old, high compression cast iron head motors need high-octane. They may also need lead, as lead compounds lubricate the valve seats. Lead compounds also increase octane rating. If they have hardend valve seats or inserts, they only need high octane, not lead, to stop pre-ignition. Old, low compression motors might have had to run leaded (e.g. old super) fuel, or lead additives, for lubrication, rather than for any performance reasons.

Modern, new, alloy head high compression motors can get away with unleaded, low octane fuels, because the aluminium heads transfer more heat away from the combustion chamber (if designed properly), reducing hot-spots that can initiate pre-ignition. The late 80's Corvette ZR1 motor could run 89 octane with a compression ratio of 11.25:1 because of this.

As mentioned, sticking in a octane booster or using higher, will not necessarily get you more power, unless you advance the ignition and/or increase the compression. Some cars have pre-ignition sensors, and will change the ignition timing on the fly to get the most out of the fuel in the tank (i.e. retard the timing until no pinging is present). It's pretty hard to increase mechanical compression on the fly, however pressurising the intake (e.g. turbocharging) effectively increases the compression (pressure ratio) inside the cylinder.

There may be slight differences in the calorific value (how much energy per kg)in fuels - that is what the dyno tuner would be seeing with his combination of 91 and 96 - more energy = more power, which is why there were some really exotic fuels in Formula 1 with normal octane ratings.

Additives shouldn't really affect the performance, as they tend to be similar across all fuels - a dye (petrol is colourless without), detergent for cleaning, antioxidants and metal deactivators to prevent the fuel degrading, corrosion inhibators to prevent tanks rusting etc. Fuel recipies may change depending on the season (e.g. to get enough vapour on a cold start), but I don't think NZ petrol does.

Any difference seen in operation is probably due to a cleaner batch of fuel, or the combustion may simply be better with a different type of fuel.

Check out Bruce Hamilton's gasoline faq: http://www.faqs.org/faqs/autos/gasoline-faq/part1/

Cheers,
FM