Shell Optimax.....performance Fuel?
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The first time I used Optimax I did think there was a difference, not much, but enough to notice. Of course this might just be "imagined" cos of the hype. The easiest way is to try it out and see what you think. I've heard some say good and some say bad.
Neil
Neil
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This pisses me off..
I find me old dear runs just a bit smoother and I would love to use it all the time ..but guess what the lovely people at shell have decided it is too good for us heathens north of carlisle..and they dont sell it up here...
I find me old dear runs just a bit smoother and I would love to use it all the time ..but guess what the lovely people at shell have decided it is too good for us heathens north of carlisle..and they dont sell it up here...
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/saabforum/images/graemlins/mad.gif
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I don't run it in the 9000 (cos its old )but I use it exclusivly (spelling?) in the Scoob - with an octane boster as well
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Defo a better fuel then standard super UL IMHO
Ian
Defo a better fuel then standard super UL IMHO
Ian
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Hmm, my nearest Shell garage is in Sutton Coldfield, which is about 7-8 miles away. I don't pass that way much, does the performance difference also equate to a large price hike over other branded high-octane unleaded fuels?
I've filled up with Optimax to give it a try. Can't say that I've noticed any difference to be honest, but then I'm still running the car in. Economy seems to be very good though - I got 35mpg average on a run from Hitchin in Bedfordshire to Gatwick Airport and back on Friday. That was with Optimax, and I was cruising at the speed limits. If I can get that sort of mileage whilst the car is still tight and new with Optimax, I don't mind paying the premium. They've got some interesting info on it at the www.shell.co.uk site. Pictures of some mucky valves versus some shiny clean ones in an competitor vs optimax comparison.
Simon
Simon
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776 Posts
Over a good few thousand miles, I have compared optimax with standard fuel. I am sure the MPG increases very slightly, if only maybe 10 miles or so on a tank of fuel. I use an octane boost, Wynns at £3.99, good for 50 litres, again improves MPG VERY slightly. Either way, have not really notice performance difference, maybe there is one, but we are fiddlers and tweakers anyweay.
However, I would like to know if this octane boost, or higher grade fuel is actually physically better for the engine, and why please ( if it is of course).
Cheers, Andy..
2.3T
However, I would like to know if this octane boost, or higher grade fuel is actually physically better for the engine, and why please ( if it is of course).
Cheers, Andy..
2.3T
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234 Posts
Andy,
As I understand it the main reason for using high octane fuel is on high proformance/high compresion engines is to do with det. ie pre detenation (spell chock pls.) using a low RON petrol the air mix will almost explode in the chamber where as high RON fuel gives a much more controled flame front giving a smother burn and more power.
Det. is an engine killer. When most turbo car ECU's detect det. they will normally wind back the available boost to stop it happening but as you would imagine the loss of boost will have an effect on proformance. Once the boost has been lowered it can take some time for the ECU to relearn its det. limits when you change back to a higher grade of fuel.
The other way to speed up the ECU re-learn is to reset it. I don't know how this works on a Saab but the standard method is to disconnect the battery overnight therefore resetting the ECU to factory default.
Now here's the thing. This is how it works on Subarus (where I have a better idea on things) cos they are designed to run on Jap 100RON fuel. With optimax being about 98RON you can see the problem.
I've not had a Saab Turbo (yet )and with Saabs being of European manufacture and therefore designed to work with poorer daily fuel the det. issue may not be so important but you will still get a benifit with higer RON.
I think I've kinda talked myself round a corner there. If anybody would like to translate that into English I'd be more than happy
Ian
As I understand it the main reason for using high octane fuel is on high proformance/high compresion engines is to do with det. ie pre detenation (spell chock pls.) using a low RON petrol the air mix will almost explode in the chamber where as high RON fuel gives a much more controled flame front giving a smother burn and more power.
Det. is an engine killer. When most turbo car ECU's detect det. they will normally wind back the available boost to stop it happening but as you would imagine the loss of boost will have an effect on proformance. Once the boost has been lowered it can take some time for the ECU to relearn its det. limits when you change back to a higher grade of fuel.
The other way to speed up the ECU re-learn is to reset it. I don't know how this works on a Saab but the standard method is to disconnect the battery overnight therefore resetting the ECU to factory default.
Now here's the thing. This is how it works on Subarus (where I have a better idea on things) cos they are designed to run on Jap 100RON fuel. With optimax being about 98RON you can see the problem.
I've not had a Saab Turbo (yet )and with Saabs being of European manufacture and therefore designed to work with poorer daily fuel the det. issue may not be so important but you will still get a benifit with higer RON.
I think I've kinda talked myself round a corner there. If anybody would like to translate that into English I'd be more than happy
Ian
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243 Posts
I would say 'don't believe the hype' myself. Tried it in the Saab, didn't realy notice any diference. However I build racing Kit cars so spend a fair amount of time at the rolling road looking for half an extra bhp - worth a try I thought after seeing the adverts.......we didn't find any improvement over normal super unleaded.
I suspect it works in the same way that washing and waxing your car makes it run better..........
I suspect it works in the same way that washing and waxing your car makes it run better..........
One of the guys that chipped up my Carlsson told me that if he couldn't get high octane fuel or a booster and he had to alter his timing (485bhp cosworth)it would cost him around 90bhp+ if he ran it without altering it....holes in the pistons
Also when I put optimax in my bike it speeds up the tick over, I am told because its a richer burn, the bike runs very smooth on it
my mpg has not changed, thats always been crappy.
Also when I put optimax in my bike it speeds up the tick over, I am told because its a richer burn, the bike runs very smooth on it
my mpg has not changed, thats always been crappy.
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I tried Optimax for the first time yesterday in my new Ducati..and definately noticed a differance, it ran a lot smoother. It's now required fuel for the Aero, the Sunbeam-Lotus and the Duke. Have to say I can't detect any noticeable improvement in performance on any of them as such, the engines just seem to run better, a lot smoother. Any performance increase might be related to an improvement to the engine/trottle response...perhaps...
Also tried it for the first time yesterday - found a garage about 3 miles from home selling it for 78.9p/ltr, filled up and drove 35 miles back home!
Noticed almost instantly a smoother idle. Boost gauge also nudges an extra mm or so redwards and doesn't taper off anywhere near as much as on crappy unleaded. Car didn't feel particularly quicker but it never does - it's only when you look at the speedo that you realise you've just broke the sound barrier
Noticed almost instantly a smoother idle. Boost gauge also nudges an extra mm or so redwards and doesn't taper off anywhere near as much as on crappy unleaded. Car didn't feel particularly quicker but it never does - it's only when you look at the speedo that you realise you've just broke the sound barrier
As per earlier threads on this subject, plus Ian (Sadlers') comments above, you shouldn't see an improvement with higher octane fuel (e.g. Optimax) UNTIL the ECU has recallibrated itself!
This necessitates a disconnected battery (allow time for capacitors to discharge, etc. 15 minutes should be enough), and then you need to do some hard accelleration runs from approx 2,000 rpm to 4,000 rpm (slightly different for autos & manuals, but this band should span both ECU requirements).
Tickover will improve irrespective of ECU recallibration as Optimax burns in a more controlled way.
This necessitates a disconnected battery (allow time for capacitors to discharge, etc. 15 minutes should be enough), and then you need to do some hard accelleration runs from approx 2,000 rpm to 4,000 rpm (slightly different for autos & manuals, but this band should span both ECU requirements).
Tickover will improve irrespective of ECU recallibration as Optimax burns in a more controlled way.
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