hello

ok i know your supposed to use super unleaded in your scoobies, on a full tank of super unleaded i usually get around 200 miles and that with octane boost in the tank aswell.
the other day i filled her up with normal unleaded by mistake and the octane boost added.
normal unleaded is 97 ron and super unleaded 99 ron.
i have actually got around 30 miles more to a full tank with normal unleaded doing the same journeys and same driving style than i would with super unleaded.
i thought with super unleaded you were supposed to get more miles than you would with normal unleaded??????????

has anyone got any explainations to this??????

 

have you been driving more carefully/slowly due to a subconscious worry about the NUL rather than SUL in the tank?

 

Normal unleaded is only 95 ron!!!!
Super unleaded is 97 ron
Only tesco 99 super unleaded and Shell Vpower are 99 ron
Prodrive always recommended using at least 97 ron fuel in cars with the ppp fitted.
Maybe you got more miles to your tank because you were aware of only haveing normal unleaded in and didnt have such a heavy right foot??

 

[QUOTE=mw2655;7826912]have you been driving more carefully/slowly due to a subconscious worry about the NUL rather than SUL in the tank?

been driving exactly the same as i usually would, i always fill up with tesco 99ron, apart from making a mistake.
i have done this before and the same thing happened.

 

drove exactly the same as always, i do usually fill up with tesco 99 ron or V power, i have done this before and the same thing happened, by the way what is ppp.

 

[QUOTE=philr;7827010]maybe the ecu is compensating for increased det or something and in turn increasing mpg from lean running?

just a thought so prob well off the mark

 

[QUOTE=johnnyroper;7827021]maybe mate, maybe, its something strange like that

 

ppp - Prodrive Performance Pack (remap, exhaust, etc)

I used to fill up with normal unleaded and never had any problems, always ran smooth with no misfires,etc
i did try SUL a few times and never found it to make any difference to the performance ( i only had aftermarket exhausts fitted so don't know the effect on a remapped car)

 

I know mine does better mpg on sul plus octane booster than on normal fuel.

DunxC

 

Mine can do 250miles to about 50ltrs or 200miles to 50ltrs, its seems to only take 2 or 3 miles of spirited drive and its down to 200miles, any more and I've seen below 1/4 in less than 150miles.

It may just be coincidance that you didnt put your foot down for them few miles while you had standard UL in.

Other reason maybe that the car is designed to run on NUL so when putting SUL in it is actually taking more fuel to create the same power as higher octane fuel take more energy to ignite them other wise they wouldn't be higher octane

(Does the '98 UK Turbo ECU do that much learning to compensate or does it just knock retard?)

Just a thought,

 

what do you mean knock retard retard the timing, maybe right about that,why petrol companys say sul gives more miles if it does not.

 

From my little knowledge on ECU's, the ECU will detect knock and retard the timing to stop it. I dont know if the ECU fitted to your car will actually advance the timing past the mapped point?

Later Denso ECU's are self learning to a degree so as well as knock retard, they will actually advance the timing (within a tolerance) if knock isn't detected until it is and then stay just behind it. From what I understand, it will allow knock once and on the second time, it will retard timing. They self learn on the fueling also for near perfect Stoich at cruising.

Some high octane fuels have flame enhibitors to promote combustion as well as preventing knock. IIRC Shell claimed that the octane boosting additives they used in Optimax did not reduce the combustability of the fuel but most oil companies are going to try there best to sell you there more expensive fuels and better MPG is hard to disprove.

 

i see what you mean now maybe when my car was remapped by prodrive,the petrol was 97ron, i usually always use 99ron, maybe i should stick with 97 ron as i seem to get more mpg and its cheaper.

 

Esso Super Unleaded is 97 RON.

When i had Andy F map the car to 99 RON he warned that anything less will cause the ECU to almost instantly retard the timing to protect the engine. However, it would take quite a while for it to 'trust' the petrol again and get back to the mapped level.

The car shouldn't advance past the mapped level so Super Unleaded, without octane booster should be fine on a UK car. Regulat (95 octane) petrol only with booster and even then it might cause the ECU to get mildly upset as it will need to mix in the tank.

5t.

 

Think I might try a tank of normal unleaded

Mine does say on the petrol flap "Use only 98 RON" or something similar.

 

i've tried measuring MPG on my 05WRX (standard) with both RUL and SUL and have found little difference. My local tesco sells RUL at 106.9 and SUL at 111.9 so for the sake of £2.50 extra per tank i give her the full beans (99ron)

 

i did not have the car when it was remapped by prodrive, i would imagine it was a few years ago when it was remapped, so i would think it would be remapped at 97 ron, i dont think 99 ron was around then in this country, was it???

 

mine has super unleaded only wrote on it

 

if the 99 ron is messing with my ecu then i would rather give her the b97 ron, even though 99 ron plus octane booster has usually been used by myself over the last year. please read the other posts, god knows

 

No the nearest was 98ish Optimax but most were 97 hence the map to that. Still not advised to use regular unleaded.

It is likely too that the map is the standard upgrade, not mapped to your car specifically so worth sticking to the right stuff chap!

5t.

 

what is the right stuff mate the 97 or 99 ron.

 

97 or 99 in yours. 97 is what prodrive work to so that should be fine. 99 is better but at the end of the day you will not get a performance benefit and no need for octane booster as it is UK not a JDM car.

Do not use 'regular' unleaded as you said in the first post though. That 95 and emergency use only.

Happy to be corrected but i'm pretty confident tha tis accurate.

 

what would all you people advise me to fill up with then, 97 ron which i seem to get more miles to the gallon or stick with the 99 ron.

 

If you get more miles on 97 stick to it.

In your 'view my scooby' it states you have a Prodrive ecu and they recommended 97 (think this was said somewhere in this anyway)

 

as the ecu is the ppp one and has a generic map for 97ron then that is what i would use.

 

I just bought my first impreza wrx last weekend - can't get enough - been confused by the type of fuel to use though (handbook says regular unleaded with 95RON+ but drivers swear by super unleaded) so rang Subaru dealer and they said regular unleaded is fine but super unleaded will increase performance. Tesco's Super Unleaded (99RON - supplied by greenergy Greenergy International Ltd) seems to be the preferred choice at the moment because of its price per litre. Will be using this....

 

I ran mine on 95 ron by accident - (when I first bought it), and the knock sensor didn't like the fuel at all. The CEL came on a lot. I now only run it on 97 Ron and it runs perfectly.

 

i think my ecu adapts to the fuel i use, i was using 99ron with octane booster, then i tried 97 ron, and for the last month or so i have only used 99ron, at first when using the 99ron alone my car kept stalling on and off for a while but now after about 150 miles it seems it has sorted itself out and does not stall anymore, it was if the car was flooding and it would not start straight away after stalling, unless i put my foot flat to floor when starting then it would start alot quicker. its spot on now anyway, the tesco up my end has now went to 95ron and a couple of pumps 99ron, while about a month ago it was 97 and 99 ron.

 

ive got a 2004 wrx standard, i always run on 95 my car run perfect,i filled up with 99 once, could not feel any difference.

 

I put in some SUL from an Esso station. Engine management light came on. Ran it out and put some V-Max in and instantly the engine management light went off.

From now on it's V-Max for me.

Mine's an 03 WRX.