What fuel to use. 95 ron or 98 ron?

Vince · 7 Apr 2011 at 14:34

Some of you may know that a few days ago I got myself a new car. The car in question is a 986 Porsche Boxster S. Today I have been doing a little reading and some places suggest that I should be using 98 ron fuel in the car whereas others suggest that the standard 95 ron is the fuel to be using.

So my question is should I be using 98 ron "optimax" fuel or similar, or should I just stick to your standard 95 ron fuel? Will it even make any difference?

NathWraith · 7 Apr 2011 at 14:35

When in doubt, "RON it up". Use 98

cm1179 · 7 Apr 2011 at 14:35

personally, i'd use 98

Vince · 7 Apr 2011 at 14:37

Hmmm so whats the advantage? fuel burns quicker is more explosive so means more power?

Lum · 7 Apr 2011 at 14:42

Actually it's less explosive, which means you can run more timing advance (more efficiency and power) without risking pre-ignition that will destroy your engine.

Also you can't get 98 RON in this country, can get 99 from Shell or Tesco and 97 from the rest.

Matt82 · 7 Apr 2011 at 14:43

read the manual.

that will tell you what fuel you want

from memory, the boxster wants high octane and peasant fuel leads to reduced performances

Virdi · 7 Apr 2011 at 14:49

That is a performance car - So you should use Super Unleaded 98+

I personally find Tesco Momentum is the best out of all the Super's

Vince · 7 Apr 2011 at 14:51

Ahh well no more peasent fuel from now on then I guess. Think I will hit up tesco tonight and fill up on 99 to see what happens. Can there really be that much of a difference? And read the manual, I don't know a man that ever read a manual for anything, period.... who reads manuals?

Bennie-Mac · 7 Apr 2011 at 14:54

Virdi said:
I personally find Tesco Momentum is the best out of all the Super's

I have never seen this available at any of the Tesco garages i have frequented, must be a backwards N.Ireland thing...

BP Ultimate seems to be it since Shell stopped supplying :/

Virdi · 7 Apr 2011 at 15:01

It used to be called Tesco 99

Vince · 7 Apr 2011 at 15:05

I will go down there tonight and see what this is all about. I have been told that if you run the car on 95 ron that the ecu adapts to this and it takes x amount of time after filling up with a higher ron fuel before you notice any difference.

Is there any truth in this?

Virdi · 7 Apr 2011 at 15:16

Yes and No.

basically - An ECU can Advance Ignition Timing when you have good quality petrol - Which results in better engine performance - i.e. your car will go a bit faster

This explains a bit:

http://www.gill.co.uk/products/digital_ignition/Introduction/9_ign_advance.asp

silversurfer · 7 Apr 2011 at 15:18

Some cars monitor for knock and alter timing accordingly I think, you would need to use up all the 95 first.

Shell has cleaning additives in it ? I think Tesco raises ron from ethanol or something similar

Is there a list of cars that can benefit from higher then 95 ron

http://www.pistonheads.com/news/default.asp?storyId=12400

Vince · 7 Apr 2011 at 15:20

Happy days, to be fair I don't think it needs to be any faster right now but if it likes this 99ron fuel better then that is what it shall have.

Firestar_3x · 7 Apr 2011 at 15:20

Much better MPGz too if you listen to Baloney Motorsports.... sorry i mean Thorney Motorsports.

Rich1988 · 7 Apr 2011 at 15:22

Unless the car is mapped for it I wouldnt bother using anything above 95, you may think there will be a difference and there may be a slight increase in mpg but it will be negligble

Firestar_3x · 7 Apr 2011 at 15:24

The car doesn't have to be mapped for it, if it's got a knock sensor it can advance or retard the timing to suit.

silversurfer · 7 Apr 2011 at 15:33

Usa fuel is like 92 Ron I think, wouldnt be surprised if it can run on 95 happily enough

Matt82 · 7 Apr 2011 at 15:34

VinceB1 said:
Ahh well no more peasent fuel from now on then I guess. Think I will hit up tesco tonight and fill up on 99 to see what happens. Can there really be that much of a difference? And read the manual, I don't know a man that ever read a manual for anything, period.... who reads manuals?

i think youll like the difference. in fact, loads of cars ive had which were "optimised" for higher octane, the difference was more than noticable when on "peasant" fuel.

plus, its only a couple quid extra per tank

Dandle · 7 Apr 2011 at 15:35

Firestar_3x said:
The car doesn't have to be mapped for it, if it's got a knock sensor it can advance or retard the timing to suit.

I thought it could only retard from what its mapped for so running super in a car mapped for 95 will not advance the timing any more. Same as running 101 in a car mapped for 98 wont give any more advance.