I cant answer your question but would suggest that you will not see any difference in performance between regular u/l and super u/l. Are you using all the revs up to the 7200 limit and using it on a track then? Some owners reckon you get a small (10%) improvement in MPG that offsets the extra cost for the super unleaded. I get 31 mpg overall average to date on reg u/l but mines still under 1k miles. What mpg are you getting and how many miles has yours done? My OPC have confirmed they use regular u/l in all their demos and cant see any reason to use Super u/l.
Where to buy 98Ron or can I use 99
- Thread starter chrisH
- Start date
InnerSphere
New member
You will likely find there is a small performance (and related fuel efficiency) benefit of using Super Unleaded (average 98 RON, can be 97,98 or 99) instead of normal unleaded (95 RON) It is very unlikely that you will feel or notice much difference between the 97,98 or 99 RON fuels. I always used Super Unleaded in my Cayman, and it definitely preferred it. I also stuck to the best 2 fuels (imho anyway) - Shell or BP. In multiple fuel tests done to date, these have proven to have the best overall performance and benefits from their additives. I suspect that if not being overly anal about it, there would be little difference between them all unless you covered very high mileages 
Enjoy your car and stop worrying about the RON rating
Enjoy your car and stop worrying about the RON rating It's not really an MPG or performance thing. It's based on the manual and what the salesman (OPC) said in that 98 RON is better for the engine though it will happily adapt. I just read an interesting review ( http://www.ciao.co.uk/Shell_Optimax_Petrol__Review_5329606 ) of OptiMax which said that the diff. between 95 and higher is that the % of petrol not being Octane, i.e. 5% for reg. UL is pentane. Apparently where Octane can be compressed (by the piston) whereas Pentane cannot so using 95 for 98 engine means the piston compresses it too much or tries too but Pentene pushes back. I guess this is the adjustment the engine makes when it detects 95 petrol or in my case 97. So, unless super perf. is wanted then 95 might be fine. Still, I wonder what the engine does for higher then 98. I guess it just sticks with 98 compression which might under use the additional octane. The article also mentioned that high octane petrol is more refine and thus cleaner.
I can't help wondering if this is all in the mind and that you are pampering your beloved Cayman. This super versus reg argument goes on whichever car you own. Porsches are fine on reg 95 U/L, if you don't believe me ask your OPC.ORIGINAL: InnerSphere I always used Super Unleaded in my Cayman, and it definitely preferred it. I also stuck to the best 2 fuels (imho anyway) - Shell or BP. In multiple fuel tests done to date, these have proven to have the best overall performance and benefits from their additives. I suspect that if not being overly anal about it, there would be little difference between them all unless you covered very high mileages
InnerSphere
New member
Of course they are fine, but they definitely are sprightlier and more fuel efficient on Super UL, so why not use it?
I've just got a Gen II Cayman. The manual and fuel cap say to use 98 Ron petrol. I've filled it up twice using Super Unleaded from Sainsburys and BP but these have both 97 RON. Looking at Shell OptiMax seems to be 99 RON.
Does anybody know where to get 98 RON petrol from?
Also, the manual (I think) plus the other places say that if the engine detects < 98 RON fuel then it changes it's how it behaves with an appropriate loss of performance. I assume this is true going from 98 to 97. However, if I were to use 99 RON, i.e. OptiMax or Tesco does the engine LIKE that and become better or perhaps worse because it's not 98.
Thanks
Does anybody know where to get 98 RON petrol from?
Also, the manual (I think) plus the other places say that if the engine detects < 98 RON fuel then it changes it's how it behaves with an appropriate loss of performance. I assume this is true going from 98 to 97. However, if I were to use 99 RON, i.e. OptiMax or Tesco does the engine LIKE that and become better or perhaps worse because it's not 98.
Thanks
Chrishazle
Active member
You're lucky - I once, years ago, put 1 tank of Tesco regular UL into my 944S - it took 2 tanks of Texaco Clean System to stop her coughing and spluttering! I've never put supermarket petrol in my Porsche since! There's enough threads on honestjohn about supermarket fuel - and I normally find I can get Shell, BP, Esso etc at the same price as supermarket (often 1p/l cheaper) around where I live. Interestingly, I do not have the same problem with diesel (shopping trolley is a MB C270CDI) - I use Tesco when I have a 5p/l discount voucher and Shell when I do not! No noticable difference in performance and MPG, and even honestjohn said supermarket diesel could be as good as major brand!
InnerSphere
New member
Sprightlier = better acceleration and responsiveness to the throttle application in general, using all available revs without using the rev limiter, on open country roads where appropriate More fuel efficient = uses less fuel, particularly on longer trips. I got between 2 and 4 mpg more using Super UL on trips of 50 miles or more. On shorter trips or mostly town driving, it only made marginal improvements to the mpg, and if I enjoyed the above mentioned sprightlier performance too much, I stopped measuring At no point did I suggest anyone needs to change their driving habits or fuel preferences. I only shared my personal experiences. Yours may vary and I am honestly not offended or intending to cause any offence I totally agree that the debate continues across brands, and I have personally had similar experiences with other brands. I find that the lower the performance or the older the vehicle in question, the less difference the Super UL makes. Turbo charged cars also seem to benefit slightly more than their normally aspirated bretheren.
More fuel efficient = uses less fuel, particularly on longer trips. I got between 2 and 4 mpg more using Super UL on trips of 50 miles or more. On shorter trips or mostly town driving, it only made marginal improvements to the mpg, and if I enjoyed the above mentioned sprightlier performance too much, I stopped measuring At no point did I suggest anyone needs to change their driving habits or fuel preferences. I only shared my personal experiences. Yours may vary and I am honestly not offended or intending to cause any offence I totally agree that the debate continues across brands, and I have personally had similar experiences with other brands. I find that the lower the performance or the older the vehicle in question, the less difference the Super UL makes. Turbo charged cars also seem to benefit slightly more than their normally aspirated bretheren.
there are many threads on this subject on the forum-do a search rather than repeat whats already been said-but basically,i believe, the cayman will cope with 95 reg ,but will retard the ignition in so doing and therefore will lower performance and increase fuel consumption-tho some may not notice this difference others definately do.apologies if this is oversimplification-as i say-pls check the relevant searches for fuller explanation by the more expert
Optimax was 98. It's V- Power now at 99. Don't think anyone does 98. 99 won't do any harm and the engine certainly won't "retard". If anything, over time, the ignition should advance slightly. I've never done any comparisons but because it says 98 on the filler flap I always put in V-Power anyway.
At Goodwood for a couple of years BP have demonstrated thier 102 octane ultimate fuel and have lots of pretty graphs that show the increased efficiency and power it delivers to a high reving engine. They claim 4 to 7.5% more power from this fuel. If they claim BP Ultimate 102 is better than using 99 instead of 98 is unlikely to do any harm. I have yet to hear of anyone using BP ultimate 102 but would be interested in doing so. Also not sure if a Cayman S would need to be retuned to use 102 or would self adjust. http://www.bp.com/genericsection.do?categoryId=6621&contentId=7017179
If the management system hasn't been mapped to adjust for the extra power potential of 99RON fuel, it will make no difference. Porsche seem to set-up to 98RON with an accepted power loss if 95RON fuel is used. Only Porsche can answer this question ... or Wayne at Chipwizards etc ?
Porsche do answer the question - it's in every Owners handbook. 98 (or more - it isn't going to hurt, so 99 in UK, or even 100 in Germany and parts of Austria!) 95 will be accomodated by retarding the timing using the knock sensors, which will result in a slight loss of performance.
I think the saleman must have been drinking 99 RON to come out with garbage like this ! RON (Research octane number) compares the antiknock properties of petrol in a test engine. 95% RON means that a fuel has the same antiknock properties as a mixture of 95%isooctane and 5%heptane. What it does not mean is that the fuel being tested is 95%isooctane. (Otherwise how could you have RON numbers of >100 !) Petrol is a mixture of branched and unbranched hydrocarbons , benzene, TBME, ethanol, detergents and other additives. The anti-knock properties of the petrol are due to the even burn of the (gaseous) fuel, with highly branched hydrocarbons raising the evenness of the burn- saying that lower RON is due to pentane (a straight chain hydrocarbon) being unable to be compressed is pure nonsense.
Posts made and opinions expressed are those of the individual forum members
Use of the Forum is subject to the Terms and Conditions
