Silvia Club of NSW

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PostPosted: Wed Aug 04, 2004 12:26 am 
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sorry chris it took too seatings for me to read all that :P

i have never run my car on anything cept optimax, same as the S13 too. i HAVE tried other fuels, BP, Caltex and Mobil, all giving me bad milage as you experienced.

If it can be believed (as it wasnt a Shell person you spoke to) and when you switch from optimax to an alternative, i didnt know it would take so many tanks to flush it out!! weird, but the other fuels had less power (to my backside) and around 80-100km less per tank

no pinging tho :)

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PostPosted: Wed Aug 04, 2004 12:31 am 
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I've generally had best results from Caltex Vortex - in smoothness of running, and overall happiness of the engine.

I've had a couple of really bad tanks of optimax in the past, and I avoid it as much as I can.

I haven't had pinging issues with any, but I'm pretty careful about that - and I tuned the car with 95 octane fuel.

With advanced timing and boost increased I'm not surprised you'd get pinging going from a 98 octane fuel to 95. You're probably getting a bit even with 98 actually.

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PostPosted: Wed Aug 04, 2004 12:33 am 
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yeah ive had one bad tank of optimax. i think it was from south westers sydney (no im not generalising here) but i mainly fill up around the corner from my house, or near the office

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PostPosted: Wed Aug 04, 2004 3:40 am 
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That's odd - I literally just switched from optimax to BP ultimate and got 550km from a tank 8)


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PostPosted: Wed Aug 04, 2004 11:09 am 
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haha i didnt know there was a tech support for fuel !

what i dont get is what he means by the ultimate is less powerful with the toulene mixed in from the optimax, wouldnt the toulene increase the octane ? toulene on its own has a much higher octane then ultimate and when mixed in i would assume it brings its octane up, also isnt toulene denser then 98ron fuel ?


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PostPosted: Wed Aug 04, 2004 11:43 am 
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maybe the toulene reacts with something in the Ultimate, whereas the Optimax is relying on it for octane boosting...?

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PostPosted: Wed Aug 04, 2004 11:49 am 
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possibly ! someone want to give optimax tech support a call :P


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PostPosted: Wed Aug 04, 2004 12:00 pm 
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yes, basically optimax is lower octane fuel with additives to boost it, but the BP and Mobil fuels are refined as 98 octane from the beginning.

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PostPosted: Mon Aug 09, 2004 4:24 pm 
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Funny? i thought optimax was the best? even croydon say to use it? i have tried other fuels but i swear optimax gives best poosh in the back? anyone agree? :-?


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PostPosted: Mon Aug 09, 2004 10:14 pm 
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Yep!

Caltex Vortex feels pretty good in the SR20DET! The car idles a bit rougher with it, but the throttle response, and the mid-range performance is quite good! It gets even better with a bit of injector cleaner added! Ha Ha!

Cheers! 8)

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PostPosted: Tue Aug 10, 2004 8:31 pm 
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Car: S13 Silvia Convertible
For info the technical help number for BP is 1300 130 127 and for Shell is 1300 134 555 (then from memory option 3 and option 2 for technical help).

I filled up the silvia on the weekend with it's second tank of Optimax after using BP Ultimate and Woolies premium and got 464km for 48Litres giving 10.3L/100km with is much better than the 11.5 average on BP Ultimate.

I phoned up the Shell technical advice to ask why I am getting such a big difference between Optimax and other 98 petrols and these are a few things he said.

Optimax had no toluene added. All petrols have toluene as a byproduct of the refining process and the higher the octane the more toluene as a by product. Toluene is Methyl Benzine and Shell sells it as an additive but it is now illegal for private people to mix petrol together. When it was legal and people did it to get better performance in rallying etc the maximum he recommended was 1 litre of Toluene in 4 litres or petrol giving a maximum of 20% toluene. Optimax is tested after refining to ensure that the % of toluene is less than 5% so there is not chance of toluene damaging the fuel system etc.

Toluene is an arromatic and shell try to keep arromatics in the petrol to minimum but it is likely that as the shell refinery is 10 years old that BP and the others who only started producing 98 much later are managing to refine 98 petrol with less toluene as a byproduct. Toluene will raise the flashpoint of petrol which makes it safer. The flashpoint of petrol is below -30 and for toluene is above 0. Butane is added to Optimax in winter for cold climates to raise the flashpoint and make cars easier to start but not in summer otherwise it is possible for cars to get vapour lock. The % of butane is changed for each area of Australia every month based on expected temperatures.

I asked about using it in the lawn mower and the fact that it seems to take forever to use up. He said that it is not a good idea to store it for too long as firstly mowers are generally hard to start and do get vapour lock in summer so using Optimax for the wrong season is likely to make the mower even harder to start. Also fuel will not go off if in a completely sealed container but there is no such thing as a completely sealed petrol container and each time you open it the air will change and it will go off. He said there is nothing wrong with pouring 2 month old Optimax into a full tank in your car and then getting some more for your lawn mower. He also thinks that storing any more than 5 litres is probably not a good idea for safety so getting a well sealed 5 litre container is the best bet.

I am not sure why my car gets a big difference between Optimax and other petrols. The only thing I can think of is that for optimax it is using the primary fuel mappings but on lower petrols it is knocking and there fore swapping to the lower safer fuel mapping. Is that is the case then chanaces are it is much better for the car to run on Optimax rather than other petrol. What is confusing is if BP Ultimate 98 is as good as everyone says then why is my economy identical using it to any 95 petrol and why the car feels the same on BP 98 and any 95 I have tried in the past. The only idea I have is that BP 98 is really BP95 and I have been ripped off. Any other ideas anyone?

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PostPosted: Tue Aug 10, 2004 9:14 pm 
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Well. BP does sell Premium unleaded (95) and Ultimate (98)

Perhaps your local dealer is playing the dodgy card?
Like Dum, i use vortex, and sometimes i hit BP.

From an tuning anecdote a while ago, i was told that the RON value of petrol decreases over time. Funnily enough, the petrol in question was also Optimax.

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PostPosted: Tue Aug 10, 2004 10:10 pm 
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Joined: Tue May 28, 2002 11:17 pm
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Car: S13 Silvia Convertible
Maybe BP in Canberra is cheating. Either way they lose as I tried four tanks from two different stations just to make sure I was getting an accurate sample and will not pay the extra for it again. I will use either Optimax or Vortex and not BP from now on. I read that soon woolies vouchers will be able to be used at Caltex stations which will make vortex better value.

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PostPosted: Wed Aug 11, 2004 1:26 pm 
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the local woolies store which i normally fill up at actually has caltex signs all over it now (used to be all green with woolies signs only) and reads caltex vortex on the pumps :D ... and people have been saying 95/96RON from vortex?... I may try mobil next time to see if there is any difference, generally speaking, fuel economy is quite good, just everyday driving.

what exactly is pinging? :oops:


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PostPosted: Wed Aug 11, 2004 8:30 pm 
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caltex vortex is advertised as 96 RON from caltex.

Pinging is detonation...on a lighter scale.

Detonation, think of it has your engine internals smashing againsts each other , alot.

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