Fuel Question

[Sandman]

When you're talking about pump gas, what octane are you talking about.
In Australia we get unleaded which is about 92 I think.
Then Premium which is 95
and Ultimate which is 98

[1outlaw]

Those numbers look like RON (research octane number). Here in "The States" stated octane is the R+M/2 (Research + Motor divided by 2)- similar to European AON (average octane number). RON is almost always much higher than Motor. I believe what most performance folks mean when they report they are running on "pump gas" is that they are running on premium 93 octane (r+m/2).

[bigjoe1]

on the west coast , we only have 91 octane= I do not think that there is much or any differance from 91 to 93 octane== I have seen quite a bit of differance from one brand to another== Chevron has been the best I have seen, and Shelll has been about the worst== ( 30 horsepower differance in one test I did several years ago. That is alot considering they cost about the same


JOE SHERMAN RACING ENGINES

[Sandman]

Thanks
I'll check up and see how it is rated here, RON or MON

[greenhj]

Its RON.

And I paid $1.35 per litre yesterday for 98ron (thats "cheap" )

[wjnielsen]

Wow, and I was feeling bad about paying half that yesterday.

-Bill

[Sandman]

So, if fuel here in Aust is RON, How does 98 octane RON compare with the 93 octane MON that you get in the US?

[KnightEngines]

Our 98 is about US 92, so their good stuff is much the same as our good stuff.

Greeny, I paid $1.42 this morning, still a bunch better than the $1.90 is was a while back.....

[1outlaw]

So, if fuel here in Aust is RON, How does 98 octane RON compare with the 93 octane MON that you get in the US?

We do not have MON (motor octane) posted here- we are MON + RON / 2 (or the average of mon and ron). Motor octane is anywhere from 5 to 10 octane #'s under RON-- thus r+M/2 is 2 1/2 to 5 numbers under the RON. Motor octane tests are done in a lab's octane engine- only a few in the country and very expensive to run tests on. RON is estimated in a lab based on gravity and distillation curves thus is cheap to do- that is likely why your country posts only RON.

[Sandman]

Awwww, c'mon. Are you saying we're cheapskates down here. haha Pay $1.49 for fuel here, that's not cheap.

When I worked at the refinery in Brisbane, they had a lab engine that has like a screw down volume pocket in the head to increase the CR while running. This was about 20yrs ago, don't know if it's still there.
Is that the type of lab engine you're talking about?

[David Redszus]

The difference between RON and MON is called fuel sensitivity. It can easily be from 8 to 12 octane points. If fuel sensitivity is 10 points, then a 93 octane index fuel is really a 98 RON, 88 MON. Since performance engines generally pay much more attention to MON, pump gas is way down on octane.

In addition, fuels with high sensitivity perform much differently than fuels with low fuel sensitivity.

The Waukesha Octane Test engine that is used by refineries to identify fuel octane, is operated in a fashion that bears absolutey no resemblence to any engine we might run. It might indicate the difference in fuel octane between two blends, it does not in any way predict how the fuel will run in a given engine.

Fuel blend octane values can be determined by use of DHA tests (Detailed Hydrocarbon Analysis) which accurately indicates the composition of a fuel blend. Knowing the octane value of each fuel component, the octane numbers can be calculated very accurately. And then are rounded off to match the stickers on the pump. When was the last time a fuel pump sticker was changed to reflect the actual octane for the current batch of fuel?

[MadBill]

... RON is estimated in a lab based on gravity and distillation curves thus is cheap to do- that is likely why your country posts only RON.

Not so! The MON and RON tests are very similar and are run on basically the same CFR (Coordinated Fuel Research) engine, as per David's post. The only real difference is RPM, mixture temperature and spark advance.

[1outlaw]

Good point. David is correct that it historically has been the Waukesha Octane Engine that was used to determine components of gas and even final blend motor octanes. The DHA method is beginning to replace the distillation curve/gravity method as state labs get funds to buy the analysers- even so the state of Wisconsin still sends out some samples to have tests run to verify the predicted octanes. If a retailer is caught cheating here the state will redtag the pump until the issue is corrected AND the violation will be posted on the web for all to see. Many states are not so agressive.