stringostar

listening to the radio the other day, and they were talking about petrol, and in particular, optimax, excellium and all the other, supposedly super unleaded fuels out there, with RON of approx 96-99. their argument was that the manufacturers are pulling the wool over our eyes, and in fact, the super unleaded is actually in fact, no better on performance, and in actually fact, is only dearer to buy per gallon than regular unleaded. a major car company, of whose name they didnt mention, filled up two cars. 1 with reg, the other with super. they ran the tanks dry over a certain run, and only found the super performed 0.7% better on MPG. so... the question in my mind, is it safe to run my 99 2000turbo AWD on regular, following what i heard on the radio?? some help needed please...

Jolly Green Monster

iTrader: (4)

they were not refering to performance cars specifically.. it is better for performance and safer to run a scoob on super

JohnD

iTrader: (5)

Sounds like a bunch of people without much clue!
Sure, on standard production cars there is little point in using super. Just about all UK cars are designed to use normal UL, even UK market Imprezas. However, performance orientated cars - especially those using turbochargers, often see some benefit from using super. If you modify the engine to increase power, it is wise to use super to keep things safe as you may be working nearer to detonation point of normal UL. Certainly, to take advantage of an ECU re-map (for power purposes - not economy map) you should use super to allow the advantage of more ignition advance.
If your car is unmodified, by all means use normal UL on a day to day basis and super on the days you know you may give it a little bit of stick?
JohnD

silent running

LOL love it. So basically you've got a bunch of people who went to all the trouble of investigating what in their minds is an issue, even doing what they probably thought was 'scientific' testing by running a single two tanks of petrol through a random model of car...yet they didn't even bother to find out what a petrol octane rating even means.

If they had done even the most cursory research into what the different octane numbers mean, they would have worked out that the 'super' in super unleaded does not claim to give petrol superhuman powers of fuel efficiency, simply denotes unleaded with a higher than standard octane rating. The main issue is whether your particular car needs it or not. If it does, use super. If it doesn't use normal unleaded, simple as that.

I also chuckle when these supposedly rigorous studies reveal all kinds of conclusions yet when it comes to it, no-one is willing to put their name to it i.e. 'a major car company'.

I'm not a super unleaded fan or anything - I use it because my car is mapped for it. I'm all for cheaper petrol and deeply resent forking out 101.9 a litre of V-Power to fuel my Scooby, while my wife's Yaris only costs 94.9p. However, the fact is that many performance cars rely on super unleaded to achieve best efficiency from their engines. I also think that the line that BP and Total have taken with their super, saying that you'll get 20-30 miles more per tank are not just very bold claims, but possibly fraudulent, but trying to claim that all high octane super unleadeds do not add to performance - just because in one anonymous car it only resulted in 0.7% fuel economy improvement - is not even science. It's pub talk and not very good pub talk at that.

It sounds like a pointless study done by clueless people.

stringostar

it was a topic in the pub last night lol! started with a guy i go drinking with, who has an 06 hawkeye, with prodrive kit (remap etc) runs it on normal unleaded and says it runs fine? make you wonder... i aint in a finacial positon to put normal unleaded in, and if the car goes bang cos i have put it in, thats me stuffed without a car i think its a load of ****e, what these researchers do... for all we know, they might even have ventured out of their conferance room to fill two cars up!!

Skooby53

iTrader: (1)

I ran my standard MY99 on normal unleaded for 3yrs after being told the label inside the fuel flap said 'super' referred to jap fuel, this was following the advice of a well know FAQ web site devoted to all things impreza. However, I have been using Super Unleaded for the past six months and it is the best thing I have done in a long time! I tried a few, supermarkets and BP Ultimate, it's hard to get anything over 98 ron where I live. The car has more urgency and is a lot smoother and picks up much quicker. I bet the people involved in this study drive Micra's !!!!

s70rjw

iTrader: (2)

Your car will run fine on regular unleaded. It will run better on SUL. Or at least thats what I found with my 00MY UK Turbo. Better response and more MPG.

scoobyjay7

so whats the difference then?
dose super burn at hire temp?
how dose this effect the ej20/25,turbo?
dose a performance car run ok on premium?
why do scoobs run better on super unleaded, what damage then to a scoob ran on premium unleaded?

Skooby53

iTrader: (1)

Ok, with my slightly limited knowledge I would say that the higher the ron number the better the fuel is, certainly for any performance car. If you use 95 ron fuel this is fine, this lets the ECU retard the timing and in so doing slightly limit the engines performance. If you use 97 ron or over the ECU will adjust the timing automatically, allowing it to be advanced slightly leading to improved performance. I think I am right in saying that the classic impreza's take a little time to adjust to the fuel change, however, this can be rectified by resetting the ECU. Check other threads for how you do this.

If using higher ron ratings such as 99ron and even the new 102 ron BP and you have any other mods you would probably benefit from having a remap done to get the best out of your car. Hope this helps a little!

dan83590

Watch...

YouTube - Facts about high octane petrol

debbiesonic

iTrader: (7)

Cars that are intended for the Japanese domestic market have the ecu programmed for a higher octane fuel than UK fuel, this allows abit more power to be extracted from the engine. Basically via the ignition timing.

Cars that are intended for the UK market have the ecu prorammed for UK fuel, no matter what car it is!

So basically, keeping it simple, If you have a stock (untampered with) UK spec car it will run fine, and safely on normal unleaded.
If you have a stock JDM car, it would be very unwise to run it on normal unleaded.

And thats it in a nutshell really!

Going onto why you're car runs better on super, well, some cars will, some cars you won't notice a difference. On most modern performance cars, the ecu is self learning, If the ecu is not reading any 'knock', it will slowly but surely advance the timing ( within it's limits) to allow a slight gain in power.
This is what the super is actually allowing.

Loosely put, poor quality fuel will cause a slight amount of knock which the ecu detects and keeps the power to safe levels to prevent engine damage.
Good quality fuel will let you're ecu advance the timing, which is where you feel the difference.

In reality there is a bit more to it, but you get the idea.

shea2k

And I think that about covers it now yeah?

If not....my conclusion:

Drive a Corsa- Fuel whatever
Drive a Focus - Fuel whatever
Drive a Micra - Erm....
Drive a Passat - Diesel (hehe)
Drive a Jap Impreza - Super Baby!

silent running

It's the sort of thing where you really need a basic understanding of how petrol engines work and can be tuned for best economy, best performance etc, before you can really understand octane ratings properly.

The most non-technical way I can put it is that the higher the octane number is, the SLOWER the fuel will burn. This sounds topsy turvey unless you know how an engine works and realise that the earlier you can fire the mixture in the cylinder before the piston reaches the top, the more efficiency you can get out of the engine, either more output or better fuel efficiency or a mixture of both. This is because the fuel-air mixture does not just explode inside the engine, it actually burns which takes an appreciable amount of time. The longer you can keep the mixture burning, before the piston gets to the top of its cylinder, the more energy you can extract from the fuel.

To cut a very long story short, the higher the octane of the fuel, the earlier you can fire the cylinder safely, leading to better performance as long as the engine's ECU is tuned for it.

ChrisGrant

102ron do they really do it???? in the UK at a BP station?

ChrisGrant

BP Ultimate UK - BP Ultimate 102 unleaded


But how much they gunna want for it????

ChrisGrant

I'll just keep posting think its about £2.40 anf the closest is MK God drive there fill up get home drive back would need to fill up again!!!!!! they should have one by prodrive!