Petrol - Which One?

Originally Posted by Razor

As Viney sez higher octanes in the winter, I fill up at Tesco most of the time.

Not that long ago our local Tesco got water in the high octane stuff. Just something worth thinking about

Higer octane fuels (IMO) give a little better sound, but I think (as other have said & Grinch has tested) there's little actual benefit, probably more of a placebo.

[Sid Squid]

Originally Posted by northwind

just using Optimax has worked for me (or whatever it's called now). The rest of the year I just use whatever's cheap

Good advice. Especially the bit about cheap, that's the right one.

Originally Posted by Viney

Find a post by Grinch, then check his blog. He done a fuel experiment over a time. Some interesting results. I find using the higer octane sutff holds back the carb icing through the winter, but use normal stuff most of the time

Over time there are no real benefits other then reduced carb icing... Over a year period with 2 different bikes I found the extra cost just about balances out the extra mileage. So unless you doing high miles like me and some other people its not worth it. If your doing lots of short trips you might find you loose the extra benefit of the higher octane fuel. Rather nicely Sainsburys in my area there Super unleaded is only 2 pence more then the normal unleaded, at 84.9 and 86.9 a litre.

The last lot of Averages where -

Averages:
BP Ultimate (97 ron):
Mpg 51.46 KM per Litre:18.21 Pence per mile:8.61 £11.87 137.7 miles
Shell Optimax (97 ron):
Mpg 52.87 KM per Litre:18.11 Pence per mile:8.27 £11.75 142.2 miles
Sainsbury's Super Unleaded (97 ron):
Mpg 51.56 KM per Litre:18.25 Pence per mile:8.12 £11.61 139.5 miles
Sainsbury's Unleaded (95 ron):
Mpg 50.37 KM per Litre:17.83 Pence per mile:8.24 £10.88 132 miles

As you can see the pence per mile is very close.

The only thing you haven't done is put them on a dyno, wonder if there's any kind of serious power deficit between the different fuels?

Also looking online on petrolprices.com and noticed this -

Name City Distance Price Last Update
Murco Doubles Garage Reading 16.7 miles 79.1p 16-01-2007
Asda Asda Lower Earley Reading 15.35 miles 83.9p 21-01-2007
Jet Chertsey Service Station Chertsey 19.66 miles 84p 21-01-2007
Bp Oak Farm Connect Farnborough 1.08 miles 84.9p 21-01-2007
Bp Green Park Connect Farnborough 1.38 miles 84.9p 21-01-2007

Can't be right can it? 79.1 ppl?

[northwind]

Originally Posted by Razor

The only thing you haven't done is put them on a dyno, wonder if there's any kind of serious power deficit between the different fuels?

One of the bike mags did that with a pair of bikes, and found they both made slightly more power, but it was a smaller % increase than the % increase in cost...

I try and only use Optimax on my car since I got it from brand new about 3 years ago.

There have been a couple of times when I used standard fuel from Asda or other petrol stations and had quite a few problems.

Boost was quite low and mpg went down a fair bit. Along with low boost other performance issues surfaced.

Worth saying my car is a 1.8 20VT with a custom map

Yep,

Only run my car on Shell V-Power (or optimax, or whatever it's called) 99Ron, or Tesco 99 Ron as a Jap import it's meant to run 100Ron, so I also use an octane booster for high days and holidays (but then it's a 2 litre flat four twin turbo with 280 hp...).

As for the SV tried super unleaded once and found it didn't feel quite as crisp, could have been my imagination as it wasn't exactly a scientific test! However if super gives more miles I may consider it as that curvy tank is a little on the small side on big mileage days.

[northwind]

Originally Posted by 600+

Boost was quite low and mpg went down a fair bit. Along with low boost other performance issues surfaced.

Worth saying my car is a 1.8 20VT with a custom map

Yeah, it'll have knock sensors- you know this I'm sure, but for the benefit of the jury Higher octane fuel detonates at higher comp/pressure, so high octane allows more boost or more advance. Some engines adapt for that- the 1.8T definately does- as do some bikes (the big mad BMW IL4 retards the ignition for lower octane fuels). But the SV's a more or less fixed system, and it's set up to run on rubbish.

Yep the scooby twin turbos tend to blow out their bottom ends with all ghe knock from lower octane fuels when on boost, or just overboosting on high octane fuel., I have been warned by some others etc on this who have suffered... The ecu also sets itself (once disconnected for a period) and teaches itself new limits with the type of fuel you're using, so there's a two fold beneifit, but as you say with no knock sensor on svs the benefits will be more limited.