Higher Octane Fuel

[the_dr38]

Is it a bad idea to use 97/98 RON fuel in my 944? I tried it once but only half a tank and obviously never felt any difference from the car and went back to 95, worried that I'd ruin the engine. But if I ran it on, say Optimax for a couple of weeks would I see a change or would I be doing more harm than good?

Regards

Lloyd

 

[Suffolk944]

Lloyd,

I dont believe you will see any benefit with the standard ecu chip in place, you would need an after market replacement that can recognise and make use of the extra RONS to achieve that. Am pretty certain that you won't have done any damage using the 97/98 RON fuel except maybe to your wallet. []

(Though of course a petrol expert may be along presently to advise us both otherwise)

 

[sawood12]

Jon is right, but if you don't mind the extra cash per tankful, which isn't really that much in reality, £3 or £4 a tank so depends on your mileage as to whether you'd notice any real difference in cost, you may as well as not is my view on it. Though you won't notice any extra power, you might see a benefit in fuel consumption, and if you use V-Power the additives in the fuel clean your engine and slow down the degredation rate of your engine oil so are actually better for your engine in the long run. Bear in mind that even though you are buying fuel of a certain RON value, by the time it has been piped all over the country, been contaminated with water, other types of fuel and sat in various holding tanks for lord knows how long, the fuel you are actually pumping into your tanks will not be to the RON value advertised - it will be something less. So by going for 97 or more RON's then at least you are probably getting at least 95 RON.

But watch out you are not getting any high RON fuels with high biofuel content (I think Tesco 99RON and BP 102 RON fuel uses biofuel to boost octane) as I don't think our cars will like it without some modifications.

On turbo's i'd say use it. Again you might not liberate any noticeable power but you will have a bit more safety margin against knock. I always tried to put Optimax/V-Power in mine, to the extent i'd drive out of my way to get it. In all my 5.5 yrs of ownership I could probably count by the fingers on one hand the number of times I used something other than Optimax or V-Power.

 

[Copperman05]

I think the theory (or marketing hype) says that having a higher octane fuel burns more efficiently therefore improving fuel economy and performance slightly, probably more obvious in performance cars than everyday runabouts. I believe these cars ecu allows the engine to run on different octane fuel by retarding ignition, etc and can run on both quite safely. Having a chipped ecu designed to take advantage of the higher octane fuel will increase the benifits of using it at the expence of poorer performance using 95RON. I dont think its high octane fuel you need to worry about but low octane fuel, these cars arent designed to be used with less than 95ron I believe. But I've never seen lower octane fuel in this country so its not something I worry about.

I know the US have a different way of measuring there fuel and the ratings are set differently, 87RON being the equivilent of our 95RON (or something simillar) which makes things somewhat even more confusing.

Edd

 

[ChasR]

I haven't come across a modern Turbo'd car that doesn't respond well to V-Power/Higher octane fuels. The VAG 1.8T engine pulls alot better in the top end with higher octane fuels.

As for other cars I am not sure. My GTi-6 ran better with V-Power but I was meant to run it on 97 anyway according to the handbook.

 

[AntB]

ORIGINAL: sawood12


But watch out you are not getting any high RON fuels with high biofuel content (I think Tesco 99RON and BP 102 RON fuel uses biofuel to boost octane) as I don't think our cars will like it without some modifications.

Always use V-Power in my 2.7 Lux.. I dunno but it just feels happier - could just be me..

Little worried on the above tho - just filled my second tank of Tesco SUL 99 as the wife had the 5p per liter off voucher things... Whats it supposed to not like...
Didnt really notice any difference on the first tank of it so I guess cant be too bad - will go back to V-Power after this tank now tho.

A

 

[PSH]

Higher octane is good for your car , well as far as the fuel that you can buy on the high street is concerned. You will notice a better throttle response if not any actual performance increase . For turbo cars each octane increase is worth 2psi in boost that the car can use before knock on a standard setting so it's very good for turbo's....[8D][8D]


Pete

 

[Eldavo]

Just make sure you don't fill up at Morrisons! They have had to removethe kite mark from their fuel as they have increased the bioethanol content to more than the British standard allows. Not a biggie for newer cars but not good for the seals and gaskets on older stuff. I know this is true for their diesel but still wouldn't risk it.

 

[ocallen]

Have always used either Tesco, BP or Shell high octane for my lux the 14 months, 8k miles, I've had it. It's done 208k miles, always starts first time, never misses a beat, often cruises 90mph+, use it in Central London regularly, often get mid 30s in mpg, several specialists who have driven it say its as good as they come ignoring the mileage. I wouldn't risk normal octane now unless I had to.

 

[DavidL]

I use it occasionally in my turbo. I cannot feel any difference in the performance but certainly get better fuel economy to the extent that if I spend the same amount of money filling up I go the same distance regardless of whether it is 95 or 97+.
I believe (but could be wrong!) that the higher octane fuel has better detergents so helps the injectors a little. Could be claptrap of course.
If it is there is no real reason to use it that I have found.

 

[sawood12]

ORIGINAL: Copperman05

I think the theory (or marketing hype) says that having a higher octane fuel burns more efficiently therefore improving fuel economy and performance slightly, probably more obvious in performance cars than everyday runabouts. I believe these cars ecu allows the engine to run on different octane fuel by retarding ignition, etc and can run on both quite safely. Having a chipped ecu designed to take advantage of the higher octane fuel will increase the benifits of using it at the expence of poorer performance using 95RON. I dont think its high octane fuel you need to worry about but low octane fuel, these cars arent designed to be used with less than 95ron I believe. But I've never seen lower octane fuel in this country so its not something I worry about.

I know the US have a different way of measuring there fuel and the ratings are set differently, 87RON being the equivilent of our 95RON (or something simillar) which makes things somewhat even more confusing.

Edd

No marketting hype here. The higher the octane of the fuel the more it can be compressed before the spark needs to kick in and initiate burning. This means the fuel air mixture is compressed that little bit more, which means more power from the expanding gasses and more force pushing the piston down therefore more torque leading to more power at the same RPM. There is a powerful effect with increased compression - it is not a linear relationship, if you can increase compression a small amount you get alot more out of the expansion of the gas therefore your 'work in' vs 'work out' ratio is improved i.e. better efficiency. Lower octane fuels will pre-ignite if you used the same ignition settings as for higher octane fuels, i.e. the air fuel mixture would explode rather than burn slowly i.e. knock.

Modern cars effectively run closed loop ignition against the knock sensor. By effectively I mean the ECU will be mapped for high octane fuel, but if knock is detected the ignition will be retarded just enough to take you out of knock and will always be trying to advance itself back to the map. Turbo's and S2's are similar, but are mapped to 95 RON (unless you've had it chipped).

So like I said earlier, if you can live with the slightly higher cost of higher RON fuel then you might as well use it.

 

[997GT3_KO]

I have just recently a '96 993 C4S - and I plan to run it SOLELY on SHELL OPTIMAX... Will feedback my experience in due course...

 

[GC8]

Virtually all 944s were intended to run on 98RON leaded fuel.

 

[pauly]

ORIGINAL: GC8

Virtually all 944s were intended to run on 98RON leaded fuel.

With a cat ?.

 

[Paz]

Sawood is right, the fuel is beneficial for our cars.

I recently had my car tweaked at Hi-Tech http://www.hitechmotorsport.co.uk/index.htm in B'ham to sort out a flat spot between 2-3K RPM, Mick sorted the fuel pressure regulator and throttle position switch liberating a few more horses much lower down the rev-range.
Anyway I told Mick I still used Miller Oils InjectaPlus http://www.millersoils.net/1s_store.cgi?product_id=143&exact_match=on&type=automotive&cart_id=9108800_32211 fuel injector cleaner despite usuing V-Power exclusively, he said that this was good practise since even the best fuels get contaminated in the tanks.

In experience V-Power (and Optimax too) has always made my previous cars run smoother and quicker.

 

[MarkK]

I am in Germany and found some 100 octane at a Garage called Aral,car seems to like it![8D]

 

[Paz]

Aral is part of BP so at a guess I'd say it's the equivalent to BP Ultimate, it's good stuff []

 

[Super_Marv]

Yeah, Aral are part of BP - the 100 Ron Aral fuel in Germany is called 'Aral Ultimate' so I guess it is their version of BP ultimate, only with 3 extra Ron for your money!

You can get 100 Ron V-Power in Germany and Austria too. It's pretty expensive in Germany though (I never found it cheaper than €1.51/litre!)

How it compares to our 99 Ron V-Power, I'm not so sure. Seemed a bit better than the Swiss 98 Ron fuel, giving a bit more power in the mid-range maybe, which helped with some steep mountain paseses.

I like with the Aral stations, that they have a small clear plastic bubble on the side of the pump for the fuel, with a wheel which turns as you fill up, so you can see the fuel which is going into your tank.

The diesel one was black, and the petrol one is lovely and clean. Interesting that they still sell 91 Ron fuel in Germany too.

Do Porsche actually recommend Super Unleaded with the 944 S2 and Turbo then? I take it they're fitted with knock sensors? I know that it's recommended with the 968. I usually put in V-Power, personally.

 

[GC8]

ORIGINAL: pauly

ORIGINAL: GC8

Virtually all 944s were intended to run on 98RON leaded fuel.

With a cat ?.

I dont know how to answer this... Surely you know very well that virtually all UK 944s did not have a catalytic converter? This being the case I think that youre being silly.

 

[944Turbo]

Could be that when they did (mine did 1990) unleaded was almost universally 96 and super only came in with the demise of leaded. However I thought they were all ok on 96 anyway.
Tony