After reading Miss WRX's report of detonation with Optimax+Octane boost, im interested to see if anyone else is getting the same problem. Im really astounded by this find especially when i read on the Shell website that Optimax is actually over 98Ron! So what could have caused this on Little Miss WRX's car? Im wondering if my MY2000 STI 6 V-LTD is suffering? Should i go to SUL????

Gez,

I have found Optimax to be fine - even in the most extreme conditions. If you are using booster I have personally found that NF is better than Millers with Optimax - don't know why as Millers with Esso SUL was very good.

Trout :D

There are a number of things which can cause detonation, apart from the fuel. I wouldn't worry about Optimax, i'm pretty sure it has been tested very well, and the fact the octane rating is higher than SUL has to be a plus.

MB

As the car has only been in the country for about 2 months now, i have only been using Optimax with NF. I havent come across any problems yet but saying that i havent compared it to SUL. But as Optimax is over 98Ron it think ile stick to that.

I have to say, I was running with Optimax and NF, but have recently stopped. My last rolling road test at Well Lane on this showed only 254 BHP, and it was detting. Recently went back to BP SUL + NF, car feels much happier, getting better MPG, and managed 270 BHP at ProSport.

Bit confused myself, as when I first started using Optimax, it felt great - some reports seem to suggest it "ages" very quickly in the tank. Also, I've heard some reports from customers that the exhaust gas temperatures go very high on Optimax, which is a bit worrying.

Correct me if I am wrong, but I have heard that it might not actually be true 98.6 RON. I am really keen to find out whether this is true or not.

Edited to say when I say it is not true 98, there are rumours - and I have no evidence for it - that it is allegedly similar to the SUL rating to start with.

[Edited by Little Miss WRX - 7/19/2002 10:19:52 AM]

I think there is too much noise in there to blame it purely on fuel. But its best to stick to what youre comfortable with. Not sure if it would account for a 15 bhp loss in performance, again, this depends on weather conditions and the road itself.

MB (confident Optimax user)

Its never going to be spot on! But will be in that ballpark.

MB

No good comparing different site RR outputs as the load set up will be different ( as will be the day conditions).
Sounds like the Well Lane set up is putting on more load and pushing the car into det.

Nick

Butty -

The rolling road comparisons I gave are probably unfair, so here are like for like :-

SUL + NF : 289 BHP, no pinking.
Optimax + NF : 254 BHP, pinking audible.

Both figures from Well Lane turbo, same operator, same rr used. The 289 BHP figure is a bit high, the air temperature was cooler, but even so.....

Personally, I trust the ProSport figure a bit more, seems closer to what I would expect from the car ( no modifications etc etc ).

At the end of the day, I going to stick with normal SF, and run a couple of tanks of Optimax through every so often, as it does seem to do a good job of cleaning out the engine. ECU resets where done before every rr figure, BTW.

:D

[Edited by BoxerFlat4 - 7/19/2002 10:23:22 AM]

I remember CraigH telling me that his STI V was not keen on Optimax.

Just remember, that just because a couple of cars are detting on it, doesn't mean that it will do it on yours!

So far the car I am driving has no problems running on it, but due to my bad experience on the fuel I am dubious about it. I therefore want to be 110% sure that the fuel won't be causing the engine problems.

I always run an import on SUL + octane booster.

http://www.scoobynet.co.uk/bbs/thread.asp?threadid=105326

Scoty

In my experience, imports are more sensitive to fuelling quality then UK models, which makes sense if you consider what they're set up to run on (100RON). The whole issue of fuel additives has been covered before by people arguing for and against octane boosters (and which one), an wether they actually raise octane or not - my suspicion is that they don't, but prevention of pinking is why I use (and sell !) boosters.

For UK cars, Optimax is probably fine, for imports, I think a "try it and see" approach needs to be taken. :D

As Dark Blue Mark said it all depends on the age of the car as well as the condition. I think one of the key factors which causes det is charge temperature. Subarus big mistake was to place such a small intercooler on top of the engine. Even a few bent fins can cause charge temp to go throught the roof thus increasing the risk of detonation. Mitsubishi did the right thing by placing it on the front but can anyone imagine an Impreza without a bonnet vent??
As miss little wrx mentioned, is Optimax really 98.6 Ron and for that is BP and Esso SUL real 97 RON. I think, and this is only an opinion, that Optimax is really 95 ron with a mixture of additives to bring it up to 98.6 ron. But can we be sure that this is not the case with BP and Esso SUL???

BoxwerFlat4, im really baffled on how 98.6Ron petrol with NF wich should be round about 100ron, gave you 254BHP. Was it a bad tank? How many tankfulls had you used before the RR session? In terms of the Pinking OK but the large power decrease baffles me. The temperature differences must have been HUGE on the day.

i have an RB5 and have been running it on different types of fuel.

Esso SUL
Shell Optimax
BP SUL

my car is completely standard (non PPP) and just under 19,000 miles.

heres wot i have found.

using optimax its runs slightly smoother when cold but havent noticed any difference other than than, i have not heard pinking from any of the fuels.
Esso SUL does seem to go further tho, (mpg)

I use optimax where i can as ev1 advises using it + there is a petrol station in bexley selling it 4 just over 71p a ltr so if i can.

Gez -

I was surprised as well ! Having said that, the 289 BHP reading may of been a fluke. Getting detting on Optimax and NF really surprised me, though. I know NF is a good booster (lets not start THAT argumnt again boys and girls !), and until then had been happy with Optimax. Give that

A. Optimax is harder to find then normal SUL
B. With the better MPG I get with normal SUL the price difference is minimal.

then I'm happy to stick with normal SUL, with the occasional tank of Optimax to "clean out" the system.

I know Steve McCullough has claimed that Optimax in the North isn't as good as in the south - not sure about this though!

Rolling roads can and will massively differ, as mentioned, there are so many variables and are useful for a guide. There may have been some slip at peak power (some roads don't pick it up). Weather may have had a significant difference, were they using cooling fans into the intercooler etc...

Just stick the fuel in and dont worry, these aren't racing cars!
Its very easy to treat them as such, but they're not too much different to anything else.

MB

Would you still do that if you knew your car was detting?????

Yep, but i'd look at other causes too :D

MB

I would too, but up until the second tank of Optimax ran through, the car was running fine, no issues.

I guess it was just conincidental that when running on Optimax it detted and when switching back to other SUL, it ran sweet. ;)

<off topic :rolleyes: >
Hey Gez,
Got the car then, got any pics, happy with Miguel and everything? Would be interested to hear your views :)
Rich
<back to optimax>
I can tell no difference in my car if I use BP/ESSO/Shell SUL or Optimax, with or without OB (Millers)

My friends GF put diesel in his WRX, might try that, seems a bit cheaper....


[Edited by RichB - 7/19/2002 11:23:24 AM]

:rolleyes: Give her a slap from me for giving females a bad name ;)

I can possibly support the theory that Optimax in the North isn't (for whatever reason) as good/pure, etc as the south (yet). When I picked up my car in Preston Alan had been running it on Optimax and it pulled like a train. I also have been running Optimax but it's nowhere near as quick now. Obviously some of this is to do with me getting used to the power having come from a brief stint with a 1.0l polo but I do think that Alan would notice the difference if he were to drive it now :(

Weather.

I don't see that you have any advantage running a UK on Optimax rather than SUL. Only a mappable ECU will take advantage of the higher octance properties by tuning in more advance.

Obviously imports should run better as it's nearer their 100 octance requirement.

All fuel deteriates over time whether it be normal UL, SUL or Optimax, I can't see that Optimax would deteriate any quicker. It's more probable that you'll notice it more as you'll be using it in a performance car. Look at most people that use normal UL, it's to fill normally aspirated cars, mostly driven conservatively, that are not reliant on good quality fuel. If you filled you nova with UL that had been sat around for quite some time I very much doubt you'd notice the deteriation where as in a car using knock control you most certainly would.

I thought that the "Optimax is really UL with additives" was purely to cover their @rses if you did find some Optimax that had deteriated, so you couldn't send a sample of for analysis to find out it's only 97.9 instead of 98.6

Hiya RichB,
Car is a Gem. I couldnt be happier with the car or Neweras service. I was a bit annoyed though when the put NUL instead of SUL. SO i whent straight to the petrol station for 97RON and a bit of Octane boost. Appart from that the SVA was carried out v-quickly and i got the car before the speficied date. Ile try email you som pics as i still dont know how to upload pics on scoobynet.

Regards

Gez

Gez,
Mail em to me and I'll host em and post em.
:)
Rich

No problem Rich, give me a chance to take a couple of good ones and ile put them throught ot you.

Gez

Guys...

Read the Evo article. If nothing else its AS GOOD as SUL but boy does it clean your valves etc nicely!!!

I put some in this morning after using UL for a while (cheaper!!). My PPP'd MY01 certainly apreciated it!!!

Jza