Fuel-- Optimax or not?

[sb-1]

Guys,
When I collected the Cayenne the salesman told me that all the normally aspirated Porkers shipped to the UK were set up to run on normal unleaded,and there was no point in using Super Unleaded/Optimax....anyone else told this....found anything to the contrary?
Steve

[superlightr]

more octane = more explosion = more power = good thing

[sb-1]

Yes I understand that ....but he said it wouldn't make any difference, performance wise to use Optimax as they are set up for unleaded..
Steve

[getcarter]

FYI - another interesting fact... I get 10% more mpg with optimax and it's less that 10% more expensive.

[agent006]

I believe he is talking from his yaris about this. Don't most (all?) modern engines adjust themselves depending on what you put in the tank?

[MauriceC2S]

Can't speak for >MY98, but 993 handbook clearly states 98 RON is required - less is OK, but you depend on the knock sensors to detect detonation and retard the ignition, losing horsepower appropriately...

OPC salesman told me exactly the same as you - its bo!!ocks..

Cheers, Maurice

[dazren]

When collecting my turbo charged car, the salesman didn't even realise that optimax had a different octane rating to super undeaded. When I pointed out the recommendation in the manual that suggests running on 98 Ron petrol he was surpised to hear super unleaded didn't have this recommened octane rating.

I believe the car has something called knock sensors that can automatically adjust according to the octane rating of the fuel. 98 Ron is the way to go on my car though.

What does the manual from the Cayenne suggest.

DAZ

>> Edited by dazren on Wednesday 17th December 10:17

[sb-1]

Daz,

Having now double checked the manual.....salesman was obviously talking out of his a*se....!

It says..'The engine is designed to provide optimum performance/consumption if fuel with 98 RON is used..'
Steve

>> Edited by sb-1 on Wednesday 17th December 10:24

>> Edited by sb-1 on Wednesday 17th December 10:25

[sb-1]

Trouble is there isn't a Shell station for miles around here!

[dazren]

Suggest a call be put in to educate the salesman concerned. He will afterall be spouting the same sh1te to all customers, some of whom do not take their driving and cars as serious as us.

Edited to say I think BP have just launched a 98+ Ron fuel to compete with optimax, have a look at the ratings on the pumps if there is one local to you.

DAZ

>> Edited by dazren on Wednesday 17th December 10:34

[GuyR]

Octane Rating is the fuels ability to resist pre-detonation (knock). A higher Octane rating does not mean that the fuel holds any more power (that is determined by other measures) it just means that for a given engine you can run more ignition advance or higher compression. It is changes in these factors that give rise to more power, not extra ‘energy’ in the fuel.

Since the ‘knock’ sensors cannot change compression ratio (obviously), when they sense detonation, they retard the ignition to reduce it and in the process lower the power.

You can put 120 octane fuel in a car mapped for 95 octane and it will not make any extra power (assuming they have the same density, oxygenation and specific calorific values etc).

What you need is multiple maps for different Octanes ie a street-map for 97 Octane and a race-map for racing fuel (I have used 106 RON Unleaded and 126 RON leaded in the past in Skylines when running 1000+ bhp in the drag-car). Although the blend of fuels and Esters can get you to the unleaded 106, any higher requires leaded, which cannot be used with catalysts and also causes massively accelerated wear on the lambda sensors.

By the way, the 126 Octane was about £5 per litre from memory and my wife complained bitterly about the 55 litre drums being stored by the kitchen. The 126 Octane is also unstable and degrades in daylight as well as being dangerous to skin.

Guy

[dazren]

GuyR said:

By the way, the 126 Octane was about £5 per litre from memory and my wife complained bitterly about the 55 litre drums being stored by the kitchen. The 126 Octane is also unstable and degrades in daylight as well as being dangerous to skin.

Crickey what some blokes have to put up with!!!

DAZ

[dazren]

www.pistonheads.com/gassing/topic.asp?t=69732&f=23&h=0&hw=optimax+BP

Steve ignore that comment about BP, their new fuel does not meet the required 98 Ron octane rating.

DAZ

[Plotloss]

In the UK.

Its 102 in certain territories by all accounts...

[Turbofree]

When I was last in Germany Optimax was being advertised as 100 octane.

[david hype]

My nearest petrol station is a Shell one. Therefore, I have always run my cars on Shell wherever possible. When they brought out Optimax I started using it and I must say that if I ever put anything else in it, the car seems slightly less responsive.

Even more noticable in the Beemer though!

[sb-1]

[quote=dazren]www.pistonheads.com/gassing/topic.asp?t=69732&f=23&h=0&hw=optimax+BP

Steve ignore that comment about BP, their new fuel does not meet the required 98 Ron octane rating.

Daz,
I think the BP Ultimate is 97 Ron but 98 in Europe!
work that out!
Steve

[dogsharks]

I'm always reluctant to take a "salesman's" word on much of anything. No offense to you sales professionals out there, it's just a fact that there are many who are less professional than you are, and they will do "anything" for a sale. Many of the people in the automotive sales business have come from selling other things, like refrigerators, and I would therefore read the manual rather than take the sales comments.

As for the "premium" fuel, It may not make the car run faster or get more milage, but it may keep the motor cleaner and better lubricated. I've always run premium fuels in premium cars for that reason. The difference in cost over a period of years is actually pretty small when you consider the other costs of owning a Porsche.

Dogsharks

[sb-1]

The cost factor isn't an issue.....I only do about 9K miles a year.....however....I have e.mailed Reading to see what they have to say on the subject.

Steve