Fuel ?

[75pno]

Hi fellow 3.2 drivers.
What fuel do you use ( no wise cracks about petrol over diesel please !)
I have read various articles from the experts, but i feel we are the experts here, so is it LRP or High octane unleaded ?
My car 89my usually drinks unleaded and to me runs better, or is that just me? I was told by a mechanic that the porsche motor is not cast iron crap but it needs its octane !!
Thanks Paul
75 Pno
very white very wide

 

[Guest]

I use 95ron with the occasional use of Optimax if I'm feeling flush. As per. 911 and Porsche World Letters April '04

 

[Guest]

Use the "Search" button on this forum, using fuel, etc.
Its all been discussed before!

 

[911sse]

I use Optimax all the time, just coz I am usually booting it somewhat.......

 

[Guest]

If you read the previous threads, you will see that the vast majority of experts agree that unleaded is fine. In fact, every 911 motor is fine with unleaded and even most 356s. Yes they like octane but will run quite happily on 95. I use Optimax for the security a little extra octane gives when running a chip.

With my mileage, I might save £20 in a year if I used cheap petrol. Even if you do a high mileage, you might save all of £100 - you do the math. Why bother with cheap fuel?

RB

 

[3.2_fordy]

I used LRP for a few years but not now after Eynsham when two of the injectors blocked up and the others in a bad way I limped home. Had new injectors fitted and the others cleaned and RLR recommended I use Optimax thay use it in there race cars so changed over what a differance it made

 

[Guest]

Why bother with cheap fuel?

I'm really puzzled about the implication that 95 Ron, being 'cheap' fuel, is in some way inferior (apart from the Ron number), and is, therefore, likely to be detrimental to the engine. Is there ANY evidence of this (apart from the advertising - great for Ferraris/what people put in their race cars etc.) ?

I have never used Optimax, and my forced aspiration engine has never complained.

So, can we have some facts, please ? I would genuinely like to know.

 

[Guest]

How about the sticker inside your fuel cap that says to use 98 octane - its what your car is designed for. I am not saying 95 is detrimental, I am just saying the saving is so trivial that I don't see the point in using something Porsche does not recommend.

RB

 

[944Turbo]

And if you get a shell loyalty card you can get some of the money back in vouchers for shops or petrol.

If your engine has a knock sensor (or it pinks under load) try some higher octane fuel.

Tony

 

[Guest]

I don't see the point in using something Porsche does not recommend.

Porsche don't recommend Optimax for my car, as it didn't exist when the car was built, just the RON rating (must check my filler cap).

My 'problem' is the fact that Optimax is not just sold as 98 RON, but as a wonder fuel (it must be, as it was designed with Ferrari in mind !). So, I believe that some of the extra cost is down to this 'special' factor.

It's not the cost issue (I use Mobil 1/Zymol), just the advertising claims that get me - how can most cars benefit from this special fuel, when they are designed to run on 95 ?

Is the American RON numbering system different to ours ? Bentley says 96 RON (min).

 

[Guest]

Posted by Early_S_Man on the Pelican Forum...

"According to the 'Bosch Handbook,' the two methods of measuring knock resistance are MON, Motor Octane Number, and RON, Research Octane Number. The MON is the more stringent test, so RON numbers are higher than MON. Thus, when the EPA and gas companies post the 'Pump Octane Number' that is calculated by averaging the two, it results in number than is less than the RON rating."

So... Pump Octane Rating in a US context is (RON + MON) /2 but in the UK it just means RON. Which means that 98 Octane (UK) is going to be the same as say 93 Octane in the US. (Roughly)

I'm with Richard.. Optimax all the time.

Cheers

Andy

 

[thboxster]

Seem to have had similar discussions before, generally resulting in the same results.

What I did do a while ago was for a set period, put in normal unleaded (doesn't matter where from) and run the car taking note of anything noticable. Then I did the same with Optimax. Twas before BP did their 97Ron offering.

The results were to say the least : not impressive.

There was little (none) difference in the engine noise, so the EMS accomodated the different fuel properly. The extra or less power was not noticable. I didn't put it on a machine as I wasn't being that scientific. But the one thing that I did notice was that Optimax improved mpg, by nearly a mile per gallon. I suspect that it would have been slightly more had I not been so heavy footed, thinking the extra power would be noticable.

The main thing though was that Shell were doing promotions with Optimax and no one else was.

 

[Guest]

To be clear, I don't think Optimax makes you go any faster (unless your car is specifically tuned for a higher octane - but then it is the change in timing that is creating hp and the octane just allows you to push further without risking knock). Go fast claims are marketing bullsh!t.

RB

 

[Guest]

Just looked in my handbook MY89.. 3.2

911 Carrera without cat - to DIN 51600, minimum 98 RON / 88 MON
911 Carrera with cat - to DIN 51607, minimum 95 RON / 85 MON

So for UK without cat it should be 98 Octane, with cat 95 Octane. In the US (if the same figures apply but they may not) with cat it would be 90 Octane (95+85)/2

Cheers

Andy

 

[Guest]

What difference would/should the cat make ? Can't affect the comp. ratio, surely, which must be the thing that is bothered by RON.

Interesting point.

Also, didn't think my engine altered it's own timing to suit the RON number. Thought this started with the 964, and their knock sensors.

If 98 UK is 93 US, then for Bentley (US) to say 96 (min), means that I would need over 100 RON here. Something wrong there.

 

[Guest]

In your second post you say Bentley says 96 RON.

If Bentley says 96 RON then this is going to mean (96+86)/2 = 91 Pump Octane in the US (assuming the MON measurement was 86)

US Octane Value on the pump = (RON measurement + MON measurement)/2

 

[Jacob]

I am obliged to use optimax thanks to Steve Wong (my chip is to be used with only 98RON).
I cannot provide you with any science on the subject - so no help there I'm afraid.
....But about a year ago BC (before chip) my car would have a loss of power at about 5000 revs, not all the time but often enough for me to worry. I went to the local indy to get a compression test and to my relief all came back well.
I asked alot of questions to alot of people and a friend asked me what fuel I was using, at the time I was using regular unleaded. He said try optimax, I did and there has been no looking back since.

 

[944Turbo]

And when Optimax was introduced it was generally cheaper than other super unleaded, though the others have come down to match it now, narrowing the gap between it and standard.
Tony

 

[carreracat]

I work in an industry where we send all our fuel off for analysis so as to ascertain if it is ok to use, we can't afford to ruin our engines with bad fuel from dodgy suppliers!
I didi the same tests with some optimax and some 95 unleaded to try to get to the bottom of the fuel saga.
A summary of the result follows:

Optimax has a higher calorific value (it has more energy per gram)
Optimax has a higher closed flash point (it wont combust under compression alone and relies on the much hotter spark to ignite it, hence no pre-ignition)
Optimax contains much less sulphur (which does not combust fully in the time allowed in a car cylinder and hence combines with the dew from the air to create sulphuric acid to eat your exhaust - even stainless!!)
Optimax contains less heavy carbon (hence less carbon deposits clogging injectors and valves)
Optimax contains NO catalytic fines (which cause excessive wear on rings, cylinders, fuel pumps and injectors)
Optimax contains more detergent additives (not sure how well these work or if they are added as a gimick - but at least they are added!)

So whether all that adds up to it being a fuel which gives you better performance is up to you to decide as you use it.
But one thing's for sure, from an engineering point of view Optimax is better for your engine in terms of reducing wear and increasing the longevity and efficiency than 95 unleaded.

Cheers

 

[thboxster]

ORIGINAL: carreracat

Optimax contains more detergent additives (not sure how well these work or if they are added as a gimick - but at least they are added!)

Bubbles out of your exhaust[]

(well someone had to say it).