Fuel Fuel Fuel!!

[Guest]

Hi,

I realise that this may already been discussed BUT do we really benefit from 98 Ron fuel?? As an average driver I think not[&:] especially at about 25p a gallon extra. I ran an experiment on my 964 tip between 95 & 98 Ron fuels and although the MPG was better by 1 over a tank the general performance was impossible to detect any difference between the 2 different fuels. I know the good [8|] book recommends 98 Ron but IMHO I think the average driver would be fine with 95 Ron. I now own a manual 993 and have done the same test and the results are much the same

What do you think?[]

 

[968er]

It has been proven that a performance car will benefit from higher octane fuel through better bhp, however, I only use it if I know that I am going to be looking for extra performance. The rest of the time 95 ron is what I use.

 

[chrisr]

Yep Ill second William , I use 95 Ron on the 993 but will put a tank of 98 in for a decent run.

Chris

 

[burrow01]

Porsche recommend 98 octane, so that is what I use - they are better engineers than I am []

As I understand it the engine is designed to run on 98 octane, but the ignition will retard under the control of the knock sensor if 95 is used ( which means a certain degree of pre-ignition has to be present before the timing will be retarded...)

I'm not sure how long the retardation of the ignition is in effect for, ie how long after you fill with 98 will it take for the ignition timing to revert to the optimum setting?

The previous owner of my car spent £6500 on an engine rebuild, and I would like to avoid that sort of bill for as long as possible [], so I follow all the Porsche recommendations.

I also use Optimax in preference to Tesco 99 Octane, to utilise the cleaning additives, although my last fill up was at over £1 per litre, so I did wince a bit....

Pete

 

[Guest]

This is something I've wrestled with during my ownership. Mine runs very well on 95 RON and I can detect no improvement in performance or mpg with superunleaded.

However, some discussion with Maurice and some other folk (elsewhere as it happens) has persuaded me that it's better - well safer actually - to use top-grade fuel. 95 RON is fine as long as the engine's knock sensor is working AOK. If it's not there's a significant risk of engine damage, and increasing over the long term.

Failing knock sensors on 993 engines is not a 'recognised' problem, but maybe it's best to play it safe. So I'm a recent convert to the super stuff.

(All the above based on my understanding of the technical issues, but I'm no engineer or scientist.)

 

[chrisr]

Interesting stuff that guys re the knock sensor .. maybe I will start using 98 RON on a regular basis if it does help engine wear in the long term

Chris

 

[MrHappy]

It really comes down to working out how much extra it would cost you over a year to use 98 instead of 95. For myself, at a max of 3,000 miles per annum, it's no more than £50 for the year - a no-brainer if ever there was one.

David.

 

[Gordon Attar]

RE 964, unless you have your car chipped then the 964 is more than happy on 95ron and was designed for it. Like all porsches put the good stuff in for trackdays or if you 'push' the car a lot.

Always remember that our US collegues are running there cars on 91-93 ron fuel.

If your cars not happy on 95 ron it will let you know and run a bit hotter I was told.

ps I run mine on 95 ron for everyday use and my specialist supports this view.

 

[Mark_Bennett]

This explains it fairly well

http://www.btinternet.com/~madmole/Reference/RONMONPON.html

 

[Gordon Attar]

Maurice

1- My understanding, gained from Rennlist is that the std US unleaded is a point or two down on ours and the quality is a bit variable by State.

2 - My specialist is Northways and you only really need the 98 RON if your are abusing your car. Tried it several times with 98 and 99 RON and could'nt tell the difference, which seems the general rule of thumb for 9 out of 10 drivers when it comes up on any of the forums. Actually I will try another tank full of Tesco's finest now that I'm more used to the car and see if I can tell the difference.

3 - Never had that problem with a Turbo, perhaps it may be an issue if I'm passing maybe 5 or 6 cars at a time.

Re Mark's note that would make 91 MON a 100 RON

 

[Mark_Bennett]

In America the service stations use the Pump Octane Number or PON rather than RON.
So 91 PON (US) ~= 95 RON (UK)

Another useful ref:
http://en.wikipedia.org/wiki/Octane_rating

 

[968er]

If, as has been said that you risk engine damage by using a RON grading that Porsche say you can use, then the manufacturer would be liable for any damage to your engine for providing incorrect information! Also, as high octane fuel is not readily available in the US, why are their cars engines not blowing up?

 

[Guest]

Surely if the handbook says it's ok to use 95 ron then no problem right? Do you not think that sometimes we look far too deep into the question asked, we could apply lots of "what about if's" to a great deal of questions raised on the forum[]

 

[968er]

Thats if you can buy it!

Its ok for all you suburbanites who have a choice of petrol stations to go to, but living in the country has its drawbacks[]

 

[Guest]

ORIGINAL: MoC2S

<snip>

'The engine is designed to provide optimum performance and fuel consumption if unleaded premium fuel, minimum 98 RON / 88 MON is used.
If unleaded premium fuels of at least 95 RON / 85 MON are used, the engine's knock control system automatically adapts the ignition timing.
.... in an emergency, on lower octane fuel (min 93 RON). Do not drive at full throttle.''

And those are genuine factory underlines ! So no ifs, just a clear staterment, you will get detonation on 95 RON, the ignition will be retarded, your power output will go down.
<snip>

Why will the ignition be retarded?

Regards

Bob

 

[968er]

As its Sunday, I shall not come back with a retort[][][]

 

[pse_SC]

What do they run on? Are they worried?

 

[Gordon Attar]

I've no English handbook, so will try a tankful, as I have a long range tank that will be £90 and will report back.

 

[Gordon Attar]

Maurice
A posting from smartgroups which helps explain why I thought they were running mainly on the equivalent of 95 ron in the US

The US uses AKI ratings which is RON+MON/2. The ROTW uses RON ratings.So US 87AKI is equivalent to 91RON euro. And 91AKI is equal to 95RON.

By the way I have filled up with 98 ron and will report back on my findings

 

[bobafett]

I have seen a more recent test with fuels, and it all comes down to how long its been in the pumps... IE old fuel whatever Ron it is = bad fuel for your car.

They rolling road tested 8 cars and 8 different fuels including a 996. The power and Knock ratings are not what you would think.

Optimax was the overall winner, though 10 days old optimax was worse than Tescos own fresh cheap motion lotion.

Sheds a bit more light on the subject.....

They added Tescos pumps are always busy, (thats why i dont go there) and optimax pumps always free. It was concluded that fresh fuel is the better fuel regardless the Ron.

I will try to dig the mag out, im sure it was Top gear.