marmski

I dont want this to turn into a 'price price price, dont buy a scoob if u cant fuel it, whine whine whine) thread, but i was wondering what the differences actually are between standard fuels to 'super' fuels that we all use.

Im a complete noob at this kinda stuff and can grasp the concept but wonder what the reality is. I have always used Optimax, when the price went up to above 100p+ i started to use the cheaper Tesco 99. I have just filled up with Sainsburys 97.

What are the differences, what will 99 do for my engine that 97 wont?

I run a standard MY05 STi, and from what i can understand it should be fine on any of these.

FYI - I can afford the car, and i can afford the fuel. I still refuse to be stiffed @ higher prices if it actually wont matter on my standard tune car.

Let me know your thoughts,

WRX_Dazza

marmski,
can "you" tell the difference???

if not, you're not driving your car how subaru intended

marmski

Well, if im honest.... soo far i havent been able too which is why i asked.

I would love to RR the car with 1 tank of fuel and then another, i cant see the difference being anymore than 10-15BHP and with UK roads where can you really notice those kinda small differences.

The car feels awesome to me no matter what fuel it has (97, 98 or 99) but that might be because i rarely have a good country road where i can open it up.

My concerns / reasons for this post was to ensure with a standard tune car that i wasnt causing any damage internally by using 97 fuel bearing in mind that at the RR i went too it demonstrated that my standard tune is running extremely rich 5k revs onwards.

myblackwrx

iTrader: (1)

If its a UK spec car it should be happy to run on 95 ul.I have a JDM import (classic) and I get better mileage out of Tescos fuel even with the fun pedal was used a bit harsher.
I guess the RR said you're car was running rich because Subaru decided to put in a safe map

bluepolarbear

If it us a UK car the answer is **** all. Performance difference between 95 SUL and 97 RON is about 100 miliseconds on the run to 60 the difference between SUL is not significant

The Branded SUL contain detegents which the marketing claim is keeps all your internals clean which in theory would mean that your car would "keep" its performance longer over time (engine power fades over time)

d5hof

i have a question; some say the optimax lasts longer. is there any truth in that or is it just a myth?

SamUK

iTrader: (1)

Its not only about keeping your engine from fading over time (1st time i have heard of this)

Do you know how Fuel Octane works? The higher the octane of the fuel the more controlled the burn hence you are able to achive better performance. Lower octane fuels such a 95ron will cause the ECU to retard your ignition timmings to keep the car at a safe level to compansate for the crap fuel you have just put in. This will also cause performance loss and eventaully kill the engine or damage it.

Finally there is a huge differnce between 95ron fuel and Optimax - get you car checked out!

But what you do is really up to you.

SamUK

iTrader: (1)

TopGear actually did this near 4 months ago. They tested on a new Subaru and it achieved near 35bhp over the standard figures quoted by Subaru using Optimax.

bluepolarbear

Yes i know how RON works. It also happens to be only one aspect of a fuel performance and not the holy grail.

The difference measured over a 0 to 60 run from using UL to SUL is measured in milliseconds - as stated in the orginal post - which you did read?

The comment regarding performance over time relates to the fact that the engine will lose performance in terms of BHP over time (specifically mileage) for a whole range of reasons. The use of branded SUL over a non branded SUL is likely to reduce that impact due to the cleaning properties of the fuel (desposits being one of the factors in reduction in performance over time).

Running a std UK car on 95ron will not cause any long term damage it will certainly not "kill" it. It has to run on it by law, yes there will be a "performance" hit but the reality is that in terms of absolute measurement eg the stop watch it is not significant on a public road. When the talking about different SUL (which are meet the same BS standard by the way) the difference is even less.

Whether you run on optimax, Ulimate, esso, texaco, Tesco 99 or Sainsbury SUL is at the end of the day a personal choice, no one product is a killer product.

If you have been fiddling under the bonnet then it is a different ball game

Gear Head

iTrader: (2)

I new UK spec sti should have a little sticker inside the filler cap saying '98ron only'.

Please don't give out cr$p info without any proof to back it up.

Wouldn't want to test the Subaru warrenty by running the sti on 95ron!!!

bluepolarbear

RTFM

"If unleaded gasoline with an octane rating of 98 or higher is not available, unleaded gasoline with an octane rating of 95 or higher may be used"

any other bit of "cr$p" info you want clarifying?

white

Why do people's CEL lights come on then when they choose a different fuel if as some people say, there is no difference or they can't feel the difference. If the CEL light is coming on then that says to me that the car is at least feeling the difference in grade even if your not.

bearded dragon

so what about a PPP'd STi? Optimax or Tesco 99? Or personal choice.
(I have had bad experiences with my WRX on BP and Sainsbury super)


I was talking to a guy at the pumps the otherday in a supra who was saying a couple of stations are now doing 102 RON (albeit at something like £2 a litre). Not sure I fancy putting this into the car though.

alex_00s

iTrader: (18)

102 RON?? Which stations do that any idea?

£2 a ltr is steep and it'd probably work out cheaper to put Tesco 99 RON in with some of that Millers Octane boost which you can buy quite cheap on eBay!

IMO tho, if your car is mapped on 97 or 99 RON then you wont experience the full benefits of a higher RON such as 102 etc. Only the truely committed will map their car on 102 RON and only ever fill it up on that... truely committed... I mean truely minted! lol!

Gear Head

iTrader: (2)

So you agree that Subaru intend for the owner to use 98ron???

Gear Head

iTrader: (2)

That is an opinion, not fact.
Please expalin to me why every tuner I speak to, advices the use of optimax/tesco99???
There is no money in it for them. The owner will be spending more money on fuel so less money to spend with the tuner, less failures due to det so more loss of earnings for the tuner etc etc.....

bearded dragon

The guy mentioned a 'couple of {Shell or BP, can't remember which} stations in Ilford for the 102 RON.

Gear Head

iTrader: (2)

Yes, BP are selling 102 ron intended for track use but legal to use on the road.
Think its around £2.50 a liter!!!
You won't see any performance benifits unless you have a remap, but then you'll have to spend £100 every time you feel up.

Woodcote

iTrader: (1)

had my scoob (2003 STi type UK) since October and have been running on Tesco super unleaded because it was cheaper that Optimax and i had no issues with that.
Now the price has gone up it is nearly as much as Optimax so as an experiment i am now running on Optimax (4th tank full now) and i can not feel any difference except my mpg has got better - only 20 or so miles a tank but better.
I would not put anything less that 98ron in because it says so on my fuel flap and as for price well its 4p a litre difference between Tesco and Shell so thats about £2 per tank more expensive for Shell but i get more miles.

Shark Man

Technically that is not 100% the whole picture. Lower octane has the tendancy to burn at a different rate than high octane (latter tends to burns slower, previous burns faster on ignition). I should stress before carrying on, that is is NOT due to the RON value itself, this purely a measurement value to resistance to autoignition. BUT the method in which fuel manufacturers use to obtain higher octane RON values. Such as the use of aromatic hydrocarbons, which are noted to affect the rate at which the fuel burns. Thus needing different ignition timing (and arguebly explaining why one fuel such as Optimax can run more ignition advance than BP Ultimate - not due to the octane, but due to the burn rate.). It's a understood concept with fuels, simply because fuel manufactures don't state the burn rate of their fuels. Technically, or in an ideal world they should all be the same. But with the varying additive packages used, this is not always the case.

So why does this matter? Well, nearly all fuels are ignited before the piston has finished going upwards to top dead centre. If it burns faster, the full explosive foce is realised before the piston has gone past TDC. It is this reason why you need to retard ignition timing as full explosive force is reached sooner after ignition with a faster burning fuel, due to the nature in which it burns. It is not just because it is "crap", it is just that it releases its full explosive potential sooner, so it needs to be ignited later (thus more retard). This does not nessercerily mean a large loss of power if the engine design is capeable of working with it. The difference beween fuels and the amount of ignition advance or knock correction values a mapper bleats on about they can run on is not the full picture. As it could well be that more retarded ignition could be the after effect of using a faster burning fuel (which is arguably better as it has less chance to detonate). Other factors such as preventing and controlling pre-ignition would be a route cause for any large loss of power between fuels.

Preignition is where the fuel ignites uncontrollably WITHOUT a spark (also referred to a dieseling for obvious reasons). This is not detonation, which is usually noted as an after effect, not the cause. Preignition is caused by lean mixtures, excessive combustion chamber temps, carboned up cylinder heads and excessive boost. It's this factor where retardation of timing must be made futher from the "ideal" value for the particular fuel your using as well as richer fuel mixtures. This factor is caused by the engine, fueling system, condition and state of tune, not soley the fuel, but increasing the RON of the fuel value would be a cheap and easy resolution (or lazy imo) to the problem.

Both preignition and a fuel that burns fast give the same symptoms: Detonation, which is what you hear (if its really bad )

Another interesting side note to power with low octane vs high octane is the calorific vaule of the fuels. It has been noted that additives used in fuels, such as detergents and to raise octane levels, not only can they slow the burn rate but they can affect the fuel's calorific value.- i.e the about of bang per litre, as the additives themselve do not have as much "bang" and through dilution, naturally it affects the overall calorific value.

As for Bluepolarbear's "branded" high octane fuels keeping your engine "clean". Well, so does the low octane brands. As pretty much all fuel manuafcturers (note manufacturer NOT retailer ) add something to their raw fuel. Be it raise octane or to help with carbon and coke despoits. Also bear in mind coking of combustion chambers is NOT due to the fuel brand, but due bad combustion. Due to the design of the engine, condition and state of tune. If your having to run mega rich fueling to combat pre-ingition, well, your going to get problems with carbon build up - obviously.

marmski

So, back on track... what will be the difference short/long term of running on 97 as opposed to 98? Does 1RON make that much difference?

Edit: Just read the above... anyone know who Manufactures Sainsburys fuel then? and where i could get info on their burn rate compared to Optimax?

I got the feeling it wasnt all about octane values....

SamUK

iTrader: (1)

Blimy...i will read this tonight when i get home....

SamUK

iTrader: (1)

would not make that much of a differnce though the quality of fuel may..

Shark Man

LOL, it's alright. It's not a direct reply to you anyway, more so something to bear in mind relating to the thread topic in general

The reason why I quoted was due to Bluebear's "detergent" thing, but that was lopped off. doh!

marmski

Ok, so the quality of Sainsburys fuel when compared to Shell/Tesco... does anyone know who supplies Sainsburys?

IIRC:
Shell = Shell (obviously )
Tesco = Greenenergy
Sainsburys = ???

Sorry to ask soo many questions, Im just cautious of 'Brand Snobbery' which perhaps the higher price stations are trying to use to their advantage.

If Sainsburys is cr$p then i wont use it again, but if their is no real reason apart from a comment like 'its cr%p' then i dont see any reason to have to pay more.

Thanks for the techy answers soo far, some really knowlegable people here and im very grateful.

GC8

Sainsbury SUL offers a good price/quality compromise if youre running a UK car (and its not too bad for 200PS-260PS imports either). If you bite the bullet and use Optimax youll see a similar improvement again over SUL and you should notice that your car runs more smoothly and returns slightly better mpg figures too.

Simon

jasonius

iTrader: (1)

My EU/UK spec 05 WRX not only states 98ron on filler cap but also in the drivers manual:

"Turbo Models

Your engine is designed to provide satisfactory performance by using unleaded gasoline with an octane rating 98 or higher. This octane rating is the Research Octane number.

If unleaded gasoline with an octane rating of 98 or higher is not available, unleaded gasoline with an octane rating of 95 or higher may be used.
Use of gasoline with an octane rating lower than 98 will detract from engine performance and driveability."

Here's a pic of the page:

http://i14.photobucket.com/albums/a3...0859Medium.jpg

bluepolarbear

In the real world - none - see orginal reply.

myblackwrx

iTrader: (1)

Chrispurvis100
I didn't know that the new imprezas had a sticker saying what fuel you should use i made the presumption that they would make it run on 95ron as that is the lowest fuel rating in this country.
Sorry

F1 CJE UK

iTrader: (8)

"anyone know who Manufactures Sainsburys fuel" its just BP Ulimate under a different name, (my dad works for BP and no we don’t get free fuel, did in the past prob 10 years ago but that’s all changed now )