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Discussion Starter · #1 ·
Dear all,
I was looking through one of the topics and someone seemed to rate Shell optimax.

I have used a couple of tankfulls of super-unleaded before and the engine did seem a bit smoother & a bit more responsive, or then again i might have imagined it.

Do you all think its worth spending the extra on optimax/super unleaded?
 

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IIRC every unit increase in Octane is equivalent to a 2-3% performance increase - so a super unleaded should give better performance. If you look at the tuning kits, they all recommend higher Octane rating for best performance.

/john
 

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Discussion Starter · #3 ·
Good answer, however the increase in energy content of the fuel is more than corrected for by the fuels increased price.

I notice next to the filler cap on my Aero it specifies super-unleaded while my wife's CSE just says unleaded.

Any more thoughts ?
 

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But that all depends on whether you have a knock sensor fitted.

I would expect turbo-equipped cars to have one so can therefore advance ignition timing in order to take advantage of higher octane fuel. My other car certainly doesn't have one so it's unnecessary expense there.

Can anyone tell me if my '93 2.0 LPT has a knock sensor?

Cheers,

Liam.
 

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Shell Optimax octane = 98Ron (I e-mailed shell to find out). But their website shows few Shell garages round here that have it. So I have not yet tried it. How much more expensive is it? Anyone tried octane boosters? I do find a significant difference when using Super unleaded (compared to Premium unleaded) in both my 1989 Carlsson and my 1999 9-3LPT.
 

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I use Optimax as a rule on my 89 Carlsson and to be honest there is little performance difference from other SUL's. I guess the benefits will be seen, or not, from prolonged use...

I have found Octane Boosters confound the knock sensors and therefore any performance improvements are neutralised....
 

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Good answer, however the increase in energy content of the fuel is more than corrected for by the fuels increased price.

I don't understand what you mean by that. I was only addressing the point about performance related to Octane rating. I was not making a comment on the price or whether it is worth it.

/john
 

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I mistakenly put Sainsbury's lead replacement fuel in my 2.3 turbo, and the performance - general running and pick-up -was markedly better. But now fuel is an amazingly cheap 69.9p/litre unleaded in Bristol cf with 75.5p/litre for the lead replacement, I don't think the present price differential merits its use.
 

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Was that a mis-type, Quarryeff? Did you mean LPG conversion ? In which case the answer is definately yes (but with some issues).

If you want fuller information, let me know and I'll post my experiences on having my '91 2.3turbo converted. Bottom line is that provided the converter knows what he's doing it can work. Performance is as good as ever, and I save £5 per 100 miles.
 

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There are specific issues with turbocharged engines and LPG. There is now an LPG system developed by Tartrini (?) an LPG kit manufacturer, that is specifically designed for the special needs of LPG systems.

My friend Patrick Merry is a Saab trained mechanic and acreddited LPG installer who now runs his own business servicing Saabs (and other cars) and fitting LPG kits. He has a Saab 9000 turbo which he has fitted LPG to and has as a demonstration car. I have driven it and I am very impressed - you would not know that you were driving on LPG if you did not know it was installed.

Contact him via http://www.amsautogas.com/
 
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