Sheepsplitter

OK after many months of evaluation I have come to the following conclusions about Optimax:-

a) In my specific car (WRX STI4 with a number of mods including de-cat and giving 348BHP on dyno) I am seeing an improvement in performance/torque/throttle response when I fill up with Optimax and do an ECU reset.
b) Performance seems to 'degrade' over a period of 10-12 tankfuls to a point where I notice that it has dropped off enough to annoy me an go and fill up with a tank of BP superplus. Withing 30-40 miles of the tank of superplus I start to get back my performance and by 1/2 tank of superplus I am back to strong performance.
On completion of the tank of superplus I fill up with Optimax again and see an even better improvement.
If fairly sure this is not just 'air-temps' or fuel quality as I always use the same fuel stop and they get new fuel weekly (I know the boss). Also I have now repeated this cycle 4 times to be sure that I'm not imagining it or having other parameters come into play.



So these are my findings, has anyone else found similar?
I'd be interested to hear from any of you who've been on Optimax and are prepared to stick a tank of Superplus through.






[Edited by Sheepsplitter - 9/13/2002 5:29:34 PM]

LoFi

I've found similar with my MY01 but always put it down the the apparent variable quality of Optimax. Others threads have suggested it degrades as it sits in the tanks at your local petrol station.

Piers LoFi

Flat 4x4

I ran almost exclusively on Optimax for 12000m (99MY+).
Since my big end was replaced (!) I've gone back to using SUL by BP or Esso. Occasionally I use Optimax and I'm sure that there is less 'sparkle' to the extent that I now seek BP garages rather than Shell.

Sheepsplitter

Bump

Sheepsplitter

Monday bump ;-)

SiPie

Spoke to Subaru at West Brom re a totally different matter but happened to mention the optimax issue having used it for 3 or 4 months. No more to say on the subject other than I now use purely SUL and will not be using optimax again.
Car now runs smoother and 'strange but true' DEFINETELY more economical.

TaviaRS

Yep, I've had the same with mine, but I've tried other things as well. Run it on NUL, change to SUL. Initially performance increases and economy improves, but then starts to drop off after about 6-10 tanks. After 5 or 6 tanks, change to Optimax, performance increases and economy improves, but then starts to drop off. Change back to SUL and guess what, it improves again. Its almost like the car gets bored of the fuel and wants a change! Works even going from Optimax to NUL which is wierd.

From preference I use BP, Esso or Total SUL, but being a Skoda the car ain't too fussy.

johnfelstead

SiPie, what did SUK say to you?

chrisp

Even my MY01 Fiesta runs better on optimax . I will keep running the RA on optimax and millers as it runs far better than SUL and millers, revs better,revs cleaner, feels liek it has more power, less spool up time, economy LOL still about 19mpg .

SiPie

John

YHM

stevenuk300

Been running MY01 UK300 on Optimax for a year now. Been reading the posts about the drop in power with Optimax so decided to put a tank of BP's SUL in. The SUL made the car feel very groggy, and jerky at low revs. Changed back to Optimax, and noticed a hell of a change.

RB5#295

SiPie,

Since I use shed-loads of the stuff (and my dealer doesn't even know what Optimax is(!)), any chance you could forward me that mail too?

TIA

Fen

SiPie

RB5...

Just had mail back from John which points out that info may not be too 'factual' to say the least. It concerned the fact that optimax was found to loose a few ron whilst lying in the tanks.
My local dealer has also reported nincreaed umbers of problems with hesitation under hard accelaration with cars and the common factor seems to be use of optimax in their opinion. I find this highly unlikey as sure shell will have tested this to death but I can only speak from experience and my MY99 now runs ALOT better and economically on normal SUL.

Sure John would be able to clarify but the bottom line was I noticed a dramatic improvement when switching to optimax then it tailed off, then I noticed improvement in performance and economy when back to SUL!!!! Who knows...!

Sorry can't be of more help
Simon

RB5#295

Thanks for that Simon, I was worried that there was some suggestion of 'Formula Shell' properties being involved again.

I actually tend to run a mix, because normally the round trip to work is further than the range of the car so I end up filling up wherever, as I don't know the area I'm in.

The nice thing with Optimax is that virtually any Shell station has it these days, and it tends to cost the same at motorway services as it does in town, even if the 95RON stuff is 3 or 4p dearer. I hate pulling into a BP / Esso / Texaco to find they don't have SUL.

As an aside the cheapest SUL I've found near my house (Optimax included) is Esso, and the pumps say 98RON...

I can't say that I've noticed huge differences dependent on fuel, but I may fill up 8 times a week and chop and change regularly, and as any Drivetrain forum regulars know my car has a problem maintaining power delivery in any case.

Fen

SCOSaltire

they all do that!

been using optimax sometimes and SUL others...

SUL is worth 10 mph on a hill that i go on...
and its smoother
and sounds better

i will still use optimax sometimes... but if i am driving hard i look for SUL...

wish Shell still sold SUL...

cant help but feel we are using the 95 ron NUL + boosters...

i smell markerting ploy... would it have had the same effect if they launched it without the Ferrari backing... ?

SiPie

Agree 100% with SCOSaltire

DJB

I've said this before but I think that Optimax exploits a fuel tax loop-hole which means that fuels higher in aromatics (such as SUL) attract a higher tax burden than NUL. I've always been convinced that although Optimax is not just NUL plus booster, it has a low aromatic content and so more of the cost of the Optimax goes to Shell and less to the Chancellor than for SUL. This is why it is cheaper than most SUL.

I've also found that the occasional tank of SUL does wonders.

D.

JohnD

iTrader: (5)

From hero to zero? I suppose if Optimax keeps the internals clean then it's still worth using?
JohnD

Flat 4x4

SiPie

Same with my 99MY - I've ditched Optimax

hades

I think my MY02 runs more economically on Optimax, but smoother on SUL. Last tank I used optimax and did ~330 miles before filling up, but the car seems a little down on power in the 20 miles I've done since.

I can't even agree with myself which is better, so can't see any hope of everyone reaching concensus!

LoFi

i'm convinced it depends on how 'fresh' the optimax is

Piers LoFi

Steve Whitehorn

iTrader: (13)

I am glad you posted this. As when I first put Optimax in I noticed a big differnce which has tailed off. Put a tank of Esso SUL in and the performance improves.
Strange - but I agree with your findings
Cheers Steve
(Modified WRX)

Sheepsplitter

I'm beginning to think that the substance(s) that Shell use to clean the engine eventually get deposited on the plugs and surounds, to such an extent that they begin to hinder the detonation in the cylinder (not talking about DET/pinking here BTW ;-)). I guess it's possible that other SUL petrols take away the deposits after a bit of time and hence restore performance.
This might not be very scientific, but I do remember EVO reviewing Optimax and saying the endoscope in the engine showed orangey deposits forming. Maybe after a lot of tanks full of fuel the deposit is quite bad for performance.

Just my 2c.

ed_the_duck

benn running on optimax since i bought me my00..I think i'll try sum sul to see if it gets rid of lag....however i notice that when filled up with 50 ltrs after a few miles it goes well until it drops below a quarter tank...could be due to vapourisation, the less fuel in the tank the vapours have more area to go to. but also i wonder is cos when you have a full tank do you get a better head of pressure??

stevenuk300

So what brand of SUL are you all using, Shell or BP?
Can't say I was that impressed with BP SUL.