MATTeL

I hope someone can help me on this one.

Does anyone have any written documentation on why we should use SUL/Optimax rather than NUL?

It would also be of use if the word performance gains did not show up at all.

The car I am driving is a MY01 with PPP.

Thanks,
Mark

sillysi

Suabru dealers can supply a graph showing the different power outputs when you use nul or sul. It is on this bbs somewhere.

Postman Pat

I run a bog std MY99 turbo. I have to confess that I thought using 95RON was Ok for the motor. Am I wrong?

PP

Beau

My UK MY99 wagon has a sticker inside the petrol flap saying "Super Unleaded Only". Seems a very good reason to only use Super Unleaded.

MorayMackenzie

I guess MattEl gets his fuel paid for by his company... lucky chap.

Moray
bbs.22b.com

DavidRB

I believe the sticker is a reference to other countries, where "super" refers to above 95 RON.

Using 95 RON (NUL) on a standard UK (not Jap import) car is perfectly ok because the ECU is designed to retard the ignition when detonation occurs. 97 RON Super unleaded (SUL) reduces the onset of ignition, so you can get more power out of each piston stroke. It's the Japanese cars with ECUs designed for 100/105 RON petrol that are unable to retard the ignition enough for our watered-down petrol, so they suffer from pinking/detonation and eventually go bang unless you use SUL + additives.

I've used both NUL & SUL in my car. SUL is more expensive, but the engine runs smoother, has more power and returns better mileage, so the added cost is pretty small.

BugEyed

Matt

As stated above, your MY01 PPP doesn't have to be run on SUL, but can be run on NUL. However, Subaru UK quote a reduction in power from 245 PS and 261 lb ft torque to 230 PS and 245 lb ft torque if you go from 97 (SUL) to 95 (NUL) octane fuel. Given you spent the money on the PPP, I suggest that you spend a little extra on the fuel to get the best from it.

Duncan

MATTeL

I am being pushed to NUL from Optimax, but I need documented evidence to prove why I should be able to stay on SUL/Optimax.

The performance gains is something I can't use as a reason for continuing with the SUL/Optimax.

The lower (relative) cost of Optimax compared to NUL and its (relatively) lower fuel consumption figures could be used.

I want to stay with the better fuel, so if anyone has Subaru/Prodive/professional documentation on the comparrisons then I would appreciate a copy.

Mark

shippd

As a newbie to this topic, can I ask whether there are any hard facts about better mpg from SUL ? If it's enough to partly compensate for the higher price, I'm sold !

DJ140

I used NUL for the first 12K miles, then switched to Optimax and have continued to use this since.

Smoother running I agree with, but I have not noticed much improvement in MPG. I record all fuel information on a spreadsheet, for tax reasons and have noticed around 1MPG better, over the last 15K miles.

Any one who tells you it does lots more to the gallon is talking CR*P

MATTeL

Thanks but I know the car runs better on Optimax, I am using it at the moment.

What I am trying to find is gard documented evidence why.