Last week I spoke to a technical manager at Subaru Customer Services. He said there is definately no performance gain using Super Unleaded on UK Standard MY99 & MY00 cars. Has any got any rolling road tests to prove this to be wrong?

I've been using SUL in MY95 for that last 1000 miles and I'm off to France next week for a blast around to EuroDisney and northen France and I'll be using SUL over there.
Using SUL I've noticed that engine pulls a lot smoother then on UL, and maybe it's just my wanting to believe but it does seem a little not a lot but a little bit quicker.
plus I seem to get more MPG using SUL.

I have notice smoother running and more free revving when using SUL. If I could get it all the time then I would always use it, the small increase in mpg just about covers the increased cost for me at least.

Brendan

Any differnce between 95 and 97RON fuel is impossible for me to detect on my MY99. When 98RON was available I thought I noticed a slight difference, but at the moment performancr, economy and smoothness are near identical. U would use Super if I attended track days for added safety, but on the road there is no real difference unless you drive a WRX/STI. In my opinion it is more important where you buy your fuel than what RON you use. Supermarket fuel is generaly crap but my favourite at the moment is BP which seems to make my car run smoother.

97RON fuel will only benifit if your car dets on 95RON. I have never heard of a unmodified UK car detting on premium 95.

There is little or no performance gain. The engine runs a little smoother, but you wont feel masses more power, because it doesnt happen.

Since changing to SUL my MY00 is definetly smoother on tick over and pulling. MPG is also better. The differences are not major however but noticeable enough for me to stick to SUL for now.

Otis.

Orville
Where do you think supermarkets get their fuel from. There isn't many oil refiners in the UK so it must come from the other major UK fuel players? BP being the biggest in the world!!

http://bbs.scoobynet.co.uk/smile.gif

Martin

I've just had my ECU reset at the Subaru garage. I've thought that if you use 95RON, the computer will set itself certain levels, but if you fill up on 97RON, then get the chip reset and then boost, it sets itself at higher levels and so increases performance. The guy at the garage said this, and also said that if I fill up with 95RON then the computer will lower its settings and reduce the performance. Anyone disagree?

Supermarkets get petrol from different companys,I've noticed that the Coop near me have had petrol from Texaco, BP and Esso
so maybe it's all mixing in the petrol tank at the garage.
But I don't know I only get petrol from garages and not supermarkets as the supermarkets aren't as cheap as the the garages

The major petrol companies have their own oil refineries whereas the supermarket and smaller petrol companies do not. They can buy the cheapest petrol going off any small refinery but the quality of that petrol can change from one refinery to the next. With the major petrol companies at least the quality of the petrol is consistant and usually better. But beware, if you pull into a BP or ESSO and find a petrol tanker in there, steer clear for a couple of days to let all the sediment in the underground tanks settle back down.

I'm with OTIS on this one. Our cars are identical, though his used to be quicker.

Otis, old chap you commented that since your ECU reset your car was slower. See you at the Midlands meet and you can drive in front of me again to "remind" your ECU to make your car faster!

This mixing of petrol and how many refineries discussion has appeared many times, do a search on the forum for "petrol" or "SUL" or something. There's tons of info.

I wouldn't say the quality of petrol from Esso and Shell was entirely consistent... I am always annoyed when I am sold a tank of bad super unleaded... you have to use it all up carefully before you can put decent stuff in. You can't spot bad fuel before it's too late. Worst of all, can you imagine getting a refund on a tank of fuel because it's bad... "sorry sir, prove it's bad and we may consider it... knocklink? whats that?"

The 'quality' (i.e. octane level) of fuel is NOT consistent at stations owned by oil companies. You will only ever find consistent fuel at supermarkets where it will be 95 RON exactly.

Refining is generally low technology (it's improving, but has a way to go) and this is complicated by the state of the oil market. The result is that refineries are constantly producing fuel at different octane levels. Each 'batch' is tested on the test engine to find the knock point and the RON is determined. Refineries generally try to produce exactly 95 RON, and will blend if possible to achieve this.

As has been stated, the supermarkets buy the cheapest fuel, at this will be the lowest RON available. This means that the higher octane stuff gets sold at the oil company's own stations at a higher cost. If the fuel makes 97 RON then it gets sold as SUL. If the fuel is less than 97 RON then it gets sold as 95 RON.

The key point is that if you buy the cheapest fuel, it will be close to 95 RON. If you buy from an oil company you might get 95 RON one day, '95.7 RON' another day, or even '96.9 RON' if you are lucky. Similarly if you buy SUL it might be higher than 97 RON, although this is less likely.

So although, as we all know, the Scooby can adjust itself to make the most of the fuel, don't forget that the 95/97 RON printed on the pump only means that the octane level is at LEAST that high, but maybe more.

I think the only real way to check this is for someone (not me) to compare performance between the cheapest 95 RON available and then go to SUL.

Hi there,

I live in the north of France and i load my scooby with belgian "SECA" 99RON SUL , is this gonna make some changes on my car than french 95/98RON ?

Mike.

I work on the 3rd floor of an office block overlooking the entrance to a Fuel depot. I can see all the fuel tankers going in and out throughout the day. I've been keeping tabs on the different tanker brand names pulling up to the same set of tanks today, since I noticed this post and this is the list:-

Shell (lots)
BP (lots)
Texaco (quite a few)
Elf (lots)
Sainsbury's (quite a few)
Tesco (a couple)
Unmarked (lots)

After remarking on this in the office I was told by a guy who used to work for BP that most of the fuel in the south of England comes from ESSO in Fawley and most of the fuel up North comes from BP Grangemouth regardless of the brand on the stations.
Apparently all the oil companies do what he called 'swaps' to reduce the distance fuel has to be driven from their own depots.
The brands to avoid apparently are the small independants who get their fuel cheeply on the spot market in Rotterdam.

Amazing what you can actually learn at work http://bbs.scoobynet.co.uk/smile.gif
Cheers, Ian.

I've had an Impreza turbo since August 95. The first was a MY 95 bought from new and run exclusively on SUL (98 RON then) for the first year. I then changed to UL because of the rapidly rising price. I'd have to admit that from the first tank-full of UL, I did notice a difference, in particular response off-boost and smoother higher rev performance. Since then I've run UL almost all the time without any problems. The difference in price is now very significant (the b****ds) due to questionable issues about carcinogenic hydrocarbons in SUL. I doubt whether any minimal economy gains come close to making up for the price difference. I think that if you want better performance you're better off changing to a performance exhaust system plus a free-flow air filter and sticking to the cheaper (albeit too-damned-expensive) petrol.

D.

BarryK,

What happened was that I changed to SUL and noticed the gains I have mentioned above. Shortly after that I fitted a Scoobysport back box and panel filter. I took it for a spin after fitting the bits and it was not so much a case of driving as hanging on!!! What a difference. I then fell into what I now would say is the ECU reset trap and the car immedistely lost it's edge. I think the ECU would have eventually settled at it's current level anyway, and by resetting it I merely helped it along and missed out on the 'honeymoon period'.

Final point is that with the bits fitted, my car is once again quicker than yours. http://bbs.scoobynet.co.uk/smile.gif

Otis.

righto!

You think u can tell the difference between a good tank and a bad tank of super unleaded? do u have a setting in your ecu where u can tell it has been knocking or detting if so thats bloomin good! http://bbs.scoobynet.co.uk/smile.gif a bit hi-tec for my ol rst. I do feel the difference between super market fuel and BP fuel BUT i have to admit that i have not used supermarket fuel since the day i decided that it definetly made a difference.

so u have a way of telling the petrol is rubbish and then just go slow for that tank? perhaps some sort of boost switch would do the trick. If the fuel is bad u could turn the boost down for now? Not sure how the ol scooby works in that dept.

anyhows..

alls very interesting. I like shell bp and esso in that order, anything else...FORGET it.

StevenRW

Otis,

What did your insurers say about the exhaust change?

Barry,

My insurers, NFU are not increasing my premiums for the ScoobySport backbox, I think Otis' are charging him a small extra premium for both mods.

Greg

Barry,

No problem at all. I think it was an extra £30.00.

Otis.

[This message has been edited by Otis (edited 19-05-2000).]

You will not notice the difference between 95 and 97RON fuels unless your car Knocks/dets. UK ECU's are programmed to reach full efficiency/performance running 95RON fuel and will not knock/det unless modified or pushed extremely hard on an extremely hot day. Fuel additives used by different companies will more likely be noticed.

According to my dealer anyway.