What fuel should actually be used? 99, 98 or 95

[Pig benis]

Thanks for all the replies everyone.

So the car is a 04 Impreza WRX, it is absolutely mint, with only 40k miles. It isn't quite an STI that I was after, but this car came up and I just had to have him. So I'd like to keep it in the best condition that I can.

As mentioned above, I am using Tesco Ultimate, where I have noticed the car will stutter ever so slightly (occasionally) on full throttle. But the car doesn't do it on BP's finest. I initally thought it was just a bad batch of fuel from Tesco, but it has done it on 2 other tanks

I am thinking of getting my car mapped very soon, is it possible to have a switchable map? One map for daily driving on 95, and then another map for running on the good stuff?

Thanks all
Vince

Edited by Pig benis on Thursday 20th October 20:04

Edited by Pig benis on Thursday 20th October 20:05

[Konan]

tonyb1968 said:

If it had running issues then super unleaded wouldn't save you, no fuel would as the ecu is getting incorrect info to start with from what ever part is faulty (MAF/O2 sensor etc)

Yes, I know. You'll see that I wrote this:

Konan said:

I wouldn't expect to see anywhere near this much pulled just for the fuel

It wasn't supposed to be an example of the timing from a WRX on 95 (although it happened to be on 95) - it had far worse problems than that! It was just a screen shot example I happened to keep because the car was in such a bad way.

You said that you wouldn't be able to tell that timing had been pulled, when obviously you can. Very easily.

[Konan]

Pig benis said:

I am thinking of getting my car mapped very soon, is it possible to have a switchable map? One map for daily driving on 95, and then another map for running on the good stuff?

There's only the one set of tables in that ECU, so I don't think so. There aren't many models of Subaru with map switching - I only know of it on some JDM Legacy.

[Ahbefive]

If you fill up your tank once a week and the difference in price between 95 and 99 is 6p per litre that equates to around £150 a year. Then you consider the economy saving may near enough negate that saving.

Why would you want to use 95?

Edited by Ahbefive on Thursday 20th October 20:40

[Pig benis]

Ahbefive said:

If you fill up your tank once a week and the difference in price between 95 and 99 is 6p per litre that equates to around £150 a year. Then you consider the economy saving may nearvenough negate that saving.

Why would you want to use 95?

You make a very valid point here, I totally agree. This is my first car that needs 99, but I wanted to make absolutely sure I was filling up with the correct octane.

All I need to do now is, replace the pea shooter style exhaust pipes on the back with something that is a bit more throaty. If anyone knows of any prodrive backboxes going, please let me know

[tonyb1968]

Konan said:

It wasn't supposed to be an example of the timing from a WRX on 95 (although it happened to be on 95) - it had far worse problems than that! It was just a screen shot example I happened to keep because the car was in such a bad way.

You said that you wouldn't be able to tell that timing had been pulled, when obviously you can. Very easily.

No you can't tell, lets say you are having a bit of fun on a country lane, on WOT, you won't notice any ignition retarding what so ever, the ecu will just adapt and then re learn, that's what its designed to do, the only way to see if you have had any det is by either running det cans or something like a KS3, either way it may not be enough for the ecu to retard the ignition.

If a car that is designed to run 95 ron fuel has issues with fuel then its not fuel or ecu related, it should happily run 95 and produce the power stated, as per my previous posts, it does not mean that you cannot run the car on super, just that the benefits will not be as high as expected (example no 20bhp gains or 5mpg extra from a tank of super v 95).

Most of these older cars have been run on everything under the sun, 95/97/8/9 ron fuel, the only cars you need to avoid are JDM imports run on 95 and STI's run on 95 ron fuel.

[tonyb1968]

Ahbefive said:

If you fill up your tank once a week and the difference in price between 95 and 99 is 6p per litre that equates to around £150 a year. Then you consider the economy saving may near enough negate that saving.

Why would you want to use 95?

Edited by Ahbefive on Thursday 20th October 20:40

Doesn't quite work that way, either way you look at it, you will be out of pocket, its a Subaru, its not going to give you great mpg to start with so on that principle that you really don't care what the mpg is, you don't give a damn about savings

[Ahbefive]

Indeed I don't care about saving 4% on my fuel costs as it is bugger all but in my S60R I certainly see 2-3mpg difference in using 99 over the couple of times I had to use 95 and the difference in power is obvious. For me this makes it a no brainer to use SUL.

My impreza I wouldn't dream of running on 95 and I won't use it on my RS either. A N/A car with less than 200bhp I might be more inclined to use the cheap stuff as generally there are no performance benefits.

[lemmingjames]

I dont know if anyone else gets this but if i use BP Petrol then usually i get the CEL warning (cruise flashing, check engine light) but with any other grade from any other brand its fine

[tonyb1968]

lemmingjames said:

I dont know if anyone else gets this but if i use BP Petrol then usually i get the CEL warning (cruise flashing, check engine light) but with any other grade from any other brand its fine

BP Ultimate? Not the greatest fuel, a few mappers recommend you stay clear of it.

[tonyb1968]

Ahbefive said:

Indeed I don't care about saving 4% on my fuel costs as it is bugger all but in my S60R I certainly see 2-3mpg difference in using 99 over the couple of times I had to use 95 and the difference in power is obvious. For me this makes it a no brainer to use SUL.

My impreza I wouldn't dream of running on 95 and I won't use it on my RS either. A N/A car with less than 200bhp I might be more inclined to use the cheap stuff as generally there are no performance benefits.

Ok lets go through this again.
OP has a 12 yr old WRX, its going to have been run on everything with no detrimental effects as its mapped for 95 ron fuel (note no detrimental effects and mapped for 95 ron fuel).
My first MY00 Impreza Turbo always ran SUL but then again I picked her up with 7 miles on the clock, had the PPP fitted at around 9k because it was too slow in standard form and most decent fwd hatches with 40+bhp less could keep up once rolling (lighter, less drag and lower traansmission losses). PPP doesnt require SUL but its recommended for maximum performance (237bhp with 95 or 250bhp with SUL). My 2 Spec C's required 99+ ( Optimax/Vpower plus millers octane plus and 97 ron as the 2nd was mapped for UK fuel). My V5 STI Type R required the same 99 ron plus octane booster as its mapped for 100 ron fuel in japan.
My latest performance car, the RCZR also runs on SUL, ive owned that since she had 4 miles on the clock, she will also happily run 95 ron and produce 270ps, but because she has such a great range out of her 55ltr tank (nearly double that of the Spec C), I dont need worry about finding where the next shell garage is.

So now you will be saying "you put sul in your cars but recommend 95 for the OP", no, im saying that the wrx isnt new and has been run on 95 to 99 ron fuel and done no harm to a car mapped for 95 ron.

If you need to put 95 in then a wrx will be happy running 95 ron, it will also run higher octane fuels but the gains will be minimal. The fact is that it can and will be happy on 95 ron fuel as that is the minimum requirement for the car, an STI or import WILL require a higher octane fuel, 97 to 100 ron, depending on the Model Year, as a MINIMUM.

[Ahbefive]

Your post assumes his car has been run on 95 for a decent portion of its life. You don't know that.

You also assume his car has not been remapped. You and possibly he also don't know that. I'd guess that 50% of impreza turbos have probably been remapped, many that owners probably don't even know about.

So lets go through this again.... for the sake of saving approx £150 a year why would you risk it?

OP's call.

[tonyb1968]

Ahbefive said:

Your post assumes his car has been run on 95 for a decent portion of its life. You don't know that.

You also assume his car has not been remapped. You and possibly he also don't know that. I'd guess that 50% of impreza turbos have probably been remapped, many that owners probably don't even know about.

So lets go through this again.... for the sake of saving approx £150 a year why would you risk it?

OP's call.

The fact is you dont know what fuel its been run on either, as for 50% being remapped, very doubtful, probably less than 20% at most, most would have just had basic mods as remaps are not cheap but 2nd hand exhausts are.

And as for what to run it on, please go read my posts.

Pig benis said:

You make a very valid point here, I totally agree. This is my first car that needs 99, but I wanted to make absolutely sure I was filling up with the correct octane.

All I need to do now is, replace the pea shooter style exhaust pipes on the back with something that is a bit more throaty. If anyone knows of any prodrive backboxes going, please let me know

Standard car.

Edited by tonyb1968 on Friday 21st October 15:45

[Ahbefive]

All speculation. Your 20% is just as pie in the sky figure as my 50% figure. Not worth the risk imo.

[tonyb1968]

Ahbefive said:

All speculation. Your 20% is just as pie in the sky figure as my 50% figure. Not worth the risk imo.

Having owned Subaru's for 14 years, you sort of get to know how many map and how many just throw a few mods on, its probably less than 20% tbh, and the OP's car is standard.

[Ahbefive]

tonyb1968 said:

Having owned Subaru's for 14 years, you sort of get to know how many map and how many just throw a few mods on, its probably less than 20% tbh, and the OP's car is standard.

I see you struggle to follow the simple points.

[tonyb1968]

Ahbefive said:

I see you struggle to follow the simple points.

No, if you READ what I have put, you get an answer. the point is, you are not getting it

[Ahbefive]

Sorry I didn't realise that you know the OP's car personally. I guess you have driven it. Did you own it at one point? If so then my mistake. If not then you still k ow nothing about it.

Looking at ebay and autotrader it looks like its more like 60-70% of imprezas have been remapped.

Your 20% figure looks even more unlikely.

But hey you win as I can't be bothered to argue with fictional figures and random made up facts. Have a nice weekend.

[vxr2010]

i bought a standard car till i found out by a boost guage and a mapper that it had been mapped , on buying it i was told honestly it had not been mapped so who knows

[tonyb1968]

Ahbefive said:

Sorry I didn't realise that you know the OP's car personally. I guess you have driven it. Did you own it at one point? If so then my mistake. If not then you still k ow nothing about it.

Looking at ebay and autotrader it looks like its more like 60-70% of imprezas have been remapped.

Your 20% figure looks even more unlikely.

But hey you win as I can't be bothered to argue with fictional figures and random made up facts. Have a nice weekend.

Yeah ok, as you are not reading anything the OP has put down, ie the exhaust is still the twin pea shooter type, which as its stupidly restrictive with that and its 3 cats, it wont be remapped as there is no benefit to be had.

And if you believe most of those adverts, remembering that they are only a very small proportion of the Subaru's out there, you wont know if its mapped or not until you take a modified, not standard car, to a mapper and get it checked out.

All you have done is said that the OP MUST run his car on sul, if you actually read my first post, post 3 on page 1, its the correct information for this car on which fuel it can run.