Blackie

Okay, the oft asked question of which premium fuel to use is upon me and after doing a search, I am still as confused as ever, due to everyone on different Octane ratings so I thought best to ask the local lads.

Anyway, I know the S2K requires Premium Unleaded and Optimax, Ultimate, and Synergy 8000 I know use RON98 fuel. However, my company fuel card can only be used at Caltex and Ampol petrol pumps, so I'm left with Vortex, which has a RON rating of 95. Does anyone here use the Vortex fuel or a RON95 equivalent on their S2K and not notice any pinging in hot weather or detriment to acceleration?

I'm in a predicament here as I don't want to put anything in her that may cause engine knock but at the same time, convenience and economics dictate I use Caltex fuel.

naishou

Vortex has always been just fine in my S2000 and WRX. There are some who say it's better fuel than Optimax and Synergy anyway, and using fuel of a higher octane rating than specified by the manufacturer of the car is of highly questionable value.

slick

I use Optimax in my S2000, and it fantastic.

In the past, and when I can't get Optimax, I have used BP & Mobil premium unleaded - RON 95.
The engine runs well on this, and does not ping etc. I would not expect it to however, as the ECU makes adjustments for fuel etc.

Having the high octane fuel really is only important when you are seriously "on it" - so for normal driving Vortex should be OK. (used that all the time in my WRX - no problems)

Cheers

naishou

There is a lot of misunderstanding about how ECUs "adjust" to different fuels. When in open loop mode, which is what applies when you're accelerating, the ECU does not tune fuel mixtures or spark advance unless it detects detonation via the knock sensors. Therefore if you run fuel of too low octane you might get pinging and the ECU will retard timing in response. This is a short term safety feature that only gets triggered when there is something wrong. Beyond this the ECU has no way of knowing what type of fuel you are using and no way of adjusting for it. There is no facility for advancing timing beyond the original presets if you put higher octane fuel in the car. What this means is that if you're not getting pinging there is no advantage to be had by using higher octane fuel per-se, although other properties of the fuel such as its energy density could affect performance and economy. Of course it can be hard to hear pinging when the ECU hears if first and retards timing, but I have heard it in my WRX when using regular unleaded (just a few taps before the ECU buts in).

Blackie

cheers guys.

RedRover

Blackie, you could buy a couple of bottles of octane booster from your local Repco shop and put one in every second fill if you're worried.

I once got caught out in the country where I couldn't find any premium and had to fill up with standard unleaded. Didn't seem to make any difference.

Austblue

I actually drive a few extra k's to get optimax partly because its a good excuse to for a drive but also because I like to stick to what I know is good. I went to a smaller local Shell when I first got the car and he didnt have optimax, only premium. He tried to tell me that there was very little difference which made me think if he was trying to bs me with this do I trust that he doesnt add ethanol? Big conclusion to jump to I know but like I said I like to stick to what I know.

My post is probably a bit o/t but my point is to say that Vortex is a top grade fuel and therefore less likely to be tampered with imo then premium at some corner store. If it feels right, stick to it.

naishou

Don't use octane boosters regularly! The manganese compound in them forms reddish deposits in upper cylinders and catalytic converters. This can increase compression, cause hot spots, ruin spark plugs and lead to more pinging than you had before using it! It can gum up catalytic converters completely. Manganese is also toxic to the brain and testes

Also Shell says that none of their branded stations sell fuel containing ethanol.

Sunder

I find that Vortex is okay as well, I get it often when I am running late and don't have time to go out of my way for Optimax. I think personally that Optimax has smoother, slightly faster power delivery. It could be in my mind though.

I used regular fuel + octane booster one time, on my way to a dyno run. I came back 10kw less at the wheels than normal. Which is reliable, because from day to day, changing temperatures and so forth, the dyno has always corrected to within about 1kw.

honda9krpm

Someone in the fuel industry once told me all of them are the same.

They all come from the same oil refinery!

There is inconsistency in performance even with the same brand. This is due to factors such as fuel tanker and fuel storage etc etc