Alex Postan
New member
Read the manual! Super unleaded.
full fat or skimmed?
- Thread starter Alex Postan
- Start date
Performance difference doubt it could be measured on day to day road driving ..... mpg may possibly be better with super duper ... Biggest difference by far could be your bank balance
http://www.quadrantvehicles.com/blog/2008/whyuse-super-unleaded-petrol.html For a car to take advantage of a super unleaded fuel it needs to be able to adjust the timing and firing of its engine via an electronic control unit (ECU). For many mainstream petrol-powered cars using high performance petrol will result in little or no improvement to the cars fuel efficiency or power output because their engine just isn’t equipped to take advantage of the higher octane fuel. Some people still feel that a higher octane fuel has better detergents included for keeping your engine healthy. This is not necessarily the case as almost all modern unleaded fuels already contain the detergents required for keeping your engine healthy. Unless the manufacturer of your vehicle recommends you use high octane petrol for your car you are just as well sticking to standard unleaded petrol which will saving money and more than likely give your vehicle the same level of performance as a higher octane fuel. 
I believe the manuals state "Your engine is designed to provide optimum performance and fuel economy using unleaded premium fuel with an octane rating of 98 RON." I think it goes on to say that it will operate properly on 95 RON if the other is not available as the engine timing will be adjusted automatically to compensate. I put V Power in the 997, for what it's worth, so can't offer an opinion as to what, if any, loss of performance or economy happens if you use the cheaper stuff.
My OPC puts regular 95 unleaded in all petrol models. Using this gives over 30 in the GEN 2 Boxster / Cayman S's. Cant believe there is any real world difference in performance or consumption in every day driving. On the track using all the top end power will be stronger in theory as the ECU will give a bit more ingnition advance, but I dont think this inquirer is into that.
nope this isn't a track day related question. the garage i normally use doesn't sell super unleaded. i've only had the cayman a week and filled up in glasgow at one of the big filling stations and put super in it as i assumed this is what it took (says 98ron on the filler cap). but yesterday i went to fill up at home at the little local station only to find they didn't sell super unleaded and had to drive 10miles on fumes to find somewhere that stocked it! then went home and read the manual to see that actually i could have put normal unleaded in it but wondered if any of you guy's actually did this or if you were all just banging the super unleaded in. it's my own fault for not checking ninja
As stated above the manual (and the filler cap) say 98. The car will retard the ignition to accomodate shorter burning petrol (95), however that will impact performance slightly. Many who have tried 98 (or 99 in the case of Shell and Tesco in the UK) have found they get better milage that compensates for the extra cost. Many use 95 because they think they are saving money - not realising that the opposite might be true! If you can't get 98 then 95 will do (I've yet to find anything other than 95 when on hols in Italy for instance!) It won't harm the car - but it is designed for 98.
Black80XSA
New member
I've tried 95/98 on at least 6 cars now, and i always get 10% better mpg on 98 - maybe it suits my driving style more, i dunno, but i can recoup the extra 5-6% cost. When i've had to put 95 in my 986 2.7 or 987 3.2 i can;t say i really noticed any difference, maybe a little more hesitency on accelerating but that could be me thinking it rather than it beiung reality. The one thing with all super unleaded fuels is to buy from a busy forecourt - they quickly lose octane rating whilst in storage, so avoid low volume selling stations.
I may give the S/UL a try as haven't done so with a Porsche but for motorway constant speed 70-80mph driving I would be surprised to see 10% improvement. Maybe if youre using a lot the rev range then it would prove a couple of %bit more efficient. Mines running in still with 500 mls up so none of that yet.
Black80XSA
New member
All my figures were based on a mixed commute of 5 miles with slightly longer weekend runs of 10-20 miles. I typically got 27/28 mpg on s/ul, and 25mpg on u/l. On the one occassion i used Tesco 99 (on a long motorway run 2-3 years ago) i got no better than when using 95 ! I drove from north to south wales in the rush hour a few weeks ago - some periods of pedal in the wilton , but a large dose of tootling along in lines of cars, snail huts and lorries - result 33mpg, not bad for a 3.2 manual []
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