Im always interested to hgere about fuels.. I did a spool on fuels with my mechanics course and I learnt that unleaded fuel is about 95-96 octance. Unleaded is about 92-94. Premium Unleaded is 96 octane. Vortex is also 96 but it is designed to clean out your injectors and fuel lines etc. Shell Optimax is 98 octane. The best fuel from my experiments is BP Ultima. I use BP ultima in all the old cars that run on LRP or Leaded fuel because the octane is better. I discovered the main reason you cant use unleaded in a leaded car is because the octance rating on unleaded is #### house. I found that a mixture of shell optimax and BP ultima was the best for performance (on any car) but as for fuel economy and performance the BP was the best all round. I found myself getting at LEAST 50kms more from BP then Shell.. running 98 premium. (in an AE86 sprinter with 4A-C motor). If I am running an old car on BP ultima all I do is up the advance on the ignition timming 3 or 4 degrees and you really notice a difference in fuel eco and performance.

I hope I helped.

discussions:
Premium Unleaded.
Confused about Lead ??

Fuel

I guess it gets a little confusing as we americans can't figure out what aussies mean by "premium unleaded". In the USA premium simply means high-octane. All street fuel here since late 1980s is unleaded (no tetraethyl lead) but with lead-replacement additives of some kind.

Has anyone else had success with the premium unleadeds? Personally I haven't found any difference in the way the car runs or the fuel economy.
Matty

Dont know about octane rating over there but i can tell you that it doesnt mean "jackshit" over here.......

I have even heard examples of random tests on so called premium unleaded fuel from the pump, with a lower octane rating then standard unleaded. My Sugestion is that if you are going racing, buy drum fuel such as ELF etc etc...........

Cheers
Peddler

i'm over in perth and my dat loves the 98 fuel runs better has better response and keeps everything in there cleaner. better fuel econemy too

Thanks for the informative note. This is quite an interesting board and I always learn something new about my old rust bucket of a car. Thanks. 87 octane it is.

Quote:This is a one-cylinder engine in a test stand. The head (IIRC) can be moved up/down over the cylinder to vary compression. Thus they can measure at what point a particular fuel starts to knock. The comrehensive initial research on octane was done in the 30s (?), but a similar test engine is still used today. For more information, search the web for "tetraethyl lead".

There are two different octane ratings: RON and MON. RON is the Research Octane Number, it is the fuels ability resist detonation during acceleration. MON is the Motor Octane Number and it is the fuels propensity to knock at high engine speeds.

The "R+M/2" is the RON + the MON divded by two, used in some parts of the world instead of one of them.

How do you measure octane rating? A special machine called a "variable compression ratio test engine" is used. Anyone have a clue how this works? I am interested.

Hope this helps

Simon

our premium unleadeds are pretty much all 98+ octane

unleadeds are bout 95

super not sure bout 95 i think

but im guessing ours and US are measured diffrent cause cars would struggle to run on 90 octane in our measurement, and their cars are rated with higer powers like japans are because they have better fuel

u know how we get detuned integras and wrxs and s15's ect ect because we have crappy fuel

Hey how do you get the octane number of fuel and what does RON stand for when talking about octane.
Thanks heaps

Damo