Which petrol?

I have had the car almost a week now and filled it up twice, but each time I have put in 95RON petrol without thinking. I am still waiting for an owners manual to be sent from the dealer, but I noticed on the inside of the filler cap that it recommends 98RON. Does anyone regularly use 95RON, or has anyone used it for extensive periods and noticed any adverse affects? The car is a daily drive for me now and I am not bothered about wringing every last bhp out of it whilst sat in traffic. I may fill it up now and then with 98RON and higher if I fancy a blast, but from an economy point of view I am happy with just 95RON. Unless, that is, I am going to cause some damage. I know that petrol suppliers claim improved mpg, with improved performance, and therefore the additional cost is balanced out, but is this true? I had an Impreza and a Z4 before the Porsche and tried the super unleaded in them both, but couldn't really tell the difference in either to be honest. Is that because the benefits are proportional to the BHP? I know some will answer this post with "you have spent a lot of money on your car, why scrimp on the price of petrol " and I accept that. However, I have read mixed views on this forum about whether or not it is possible to run it on 95RON and would like to know more.

unless you have a problem getting super i think you need to weigh up the cost differance its about 4 p per litre around here worse 20 p a gallon as my cars not a daily i use average 10 gallons a week £2 a week £100 ish a year on a 30k car its nothing not tried the porsche on 95 but when i run my audi on 95 i get 35-36 on 97 its 37-38 so the cost per mile is around the same just my opinion Rob

I normally use Tesco 99 RON. A couple of times I have put in 95 RON and with the same driving the car returns 3-4 mpg less.I think that by using the 99 RON the engine is more effecient and will probably last longer.

You can use 95,98,99 or 100 RON because the engine has a knock sensor fitted which will alter the fuelling accordingly. Many people don't know this and those that do would maybe too scared to try but the 996 along with many other cars would actually run ok on EP85 (Ethanol) I tend to use mainly Tesco 99RON but if in a desperate situation I will use 95/98 and if up Donny fill her up on 100 uh: The higher the RON the hotter the burn = more power which inturn means higher MPG so therefore the calulation works out about the same (this calculation excludes 100 from Donny because that needs mortgage facillities!)

Impreza would probably need an ECU reset - most models AFAIK have a 'learning' CPU (mine does) and would adjust engine settings to suit the lowest RON it had received, and would keep them there regardless of an occasional tankful of higher RON. Looks like you missed-out on the Imprezas true performance.

its all relative really you may think you are saving a couple of pence per litre using 95RON however you get better MPG with 98/99RON so it balances out, plus using 98/99 you are complying with porsches recommendation.

It was clearly worth asking the question. I just wanted to be sure that the higher RON fuels did return a higher mpg and that it wasn't just marketing hype. But it sounds like most of you are convinced that you are actually getting higher mpg, which is good enough for me. Thanks

I thought the ECU learnt over time, so putting 95 in at one time and then switching to 98/99 would see benefits as the ECU adjusted back up over a few tankfuls?

there is an ECU reset using the ign key , i think you turn on but don't start leave 1 min then turn back off then start as normal some one will confirm this Rob

shell vpower I use shell vpower. some research suggested that this was the best fuel. Tesco uses ethanol in its fuel mix. Jeremy

Re: shell vpower +1 V-power every time

Re: shell vpower IME, different cars suit different petrol. However, some documented research suggests that Tescos is slightly better. http://www.thorneymotorsport.co.uk/tuning/Fuel_Test_Results_Update.shtml Tescos does use ethanol, correct. V-power also has 5% ethanol as it's 'bio' component, as specified by the RTFO (renewable fuel transport obligation) legislation.

I have always used V-Power, Tesco 99 or equivalent in my Porsches, except for the odd occasion that it has not been available. I actually did try and do a comparison once, but without driving the same roads at the same speeds it's almost impossible to tell... I think there may have been a slightly improved mpg with the higher octane rating :?: However, I definitely did notice a difference in performance (and that's probably why I struggled to significantly improve mpg! :grin: ) At the end of the day, the car is designed to run most efficiently on 98 octane, so it will either give you better mpg or better performance (but probably not both at the same time :thumb: ) Consistently using the lower octane could also lead to further inefficiencies from valve seat damage, etc. (Actually - that has got me thinking... I wonder if any of the cylinder liner failures are connected to running lower octane fuels? :dont know: )

Hi OC, Does the 964 and 993 have an automatic learning CPU where you change fuel grade and forget about it and the ignition settings will advance/retard automatically. I have heard that you have to do a manual reset?.... Any idea how this would be carried out?.

I don't think the 993 retains any 'memory' - AFAIK it simply reacts instantly to any 'pinking' and advances/retards the timing all the time.... the best system IMO. However, to try and clear out any 'memory' if there is one, you could try disconnecting the battery for a day or so. I'll do a search on rennlist - those crazy americans will know. The Impreza has an explicit way of resetting the CPU/ECU, and boy does it make a difference.