Is it just me or does Optimax. . . .
Discussion
After reading this, that and the other about Optimax, I thought I'd try it for the first time.
I put £ 15.00 worth in this evening and went for a quick blast. (Quick being the operative word!)
Is it just me or does this fuel make your cars quicker. I cant make my mind up whether I've been brainwashed but I felt quite surprised at the very noticeable difference.
I put £ 15.00 worth in this evening and went for a quick blast. (Quick being the operative word!)
Is it just me or does this fuel make your cars quicker. I cant make my mind up whether I've been brainwashed but I felt quite surprised at the very noticeable difference.
It's a strange one this. I tried about 4 tankfuls of the stuff and noticed a drop in performance and a slight increase in engine noise. Same went for Super Unleaded. Run it on standard unleaded and it's a different motor again, wierd. It may be due to the car's setup or the ECU, I don't really know, but it seems to sit at odds with the majority of opinion.
Andy
Andy
Dan said: Might be talking out my ar$e here but I thought the car was tuned with an octane rating in mind (i.e. whatever is in the tank) and therfore will probably not run so well on richer or leaner fuel.
I'm sure someone will correct me....
No Dan you are spot on (there is a great article in this months Sprint about higher octane fuels) in order to get the most from a higher octane the engine needs to be mapped/tuned to run that fuel. A car tuned to run on 95 octane fuel will not noticeably increase in performance if you dump a tank full of 98 octane in . To get the best the engine can be tuned closer to ‘detonation’ i.e. tuned for high power due to a better air/fuel mix from the higher octane. This is why the Cerbera’s have the 95 and 98 octane options at the push of a button, the car having two fuel maps each optimised for their respective octane ratings.
Also with high street fuels the octane level can vary, notice on the Shell gumpff it says guaranteed to a minimum octane level ….. race fuels are produced to a much stricter octane rating this means that engines using the race fuel regularly can be tuned even better as they do not need to take in the variance of high street fuels.
Optimax is supposed to be 98.4.
But yes - as has been stated - unless your car can recognise it is running on higher octane fuel and advance its timing OR its been manually advanced with a tank full of high octane fuel on a rolling road (like my Golf - in which case you must ALWAYS run the higher octane stuff) - you won't get any benefit out of Optimax.
Many modern cars have knock sensors to detect lower octane fuel and back off the timing but not the other way round.
By the way I run Optimax PLUS an octane booster in the Golf.
But yes - as has been stated - unless your car can recognise it is running on higher octane fuel and advance its timing OR its been manually advanced with a tank full of high octane fuel on a rolling road (like my Golf - in which case you must ALWAYS run the higher octane stuff) - you won't get any benefit out of Optimax.
Many modern cars have knock sensors to detect lower octane fuel and back off the timing but not the other way round.
By the way I run Optimax PLUS an octane booster in the Golf.
Dan said: Might be talking out my ar$e here but I thought the car was tuned with an octane rating in mind (i.e. whatever is in the tank) and therfore will probably not run so well on richer or leaner fuel.
I'm sure someone will correct me....
That seems to be what I was thinking, but I wasn't sure. My 13yr old 2.9EFi AFAIK doesn't auto sense and has been set up for unleaded, so fits in nicely with the results. However, a lot of the S series guys do claim better performance on the same engine, but I can't confirm if they have all been remapped or not.
Thanks for sorting that one out guys, you learn something new every day on here.
Andy
My Golf GTI had no electronic ignition or anti-knock systems and was advanced a bit too far for unleaded. Running on Optimax made a huge difference - no more pinking in midly warm weather, pulls loads cleaner with much faster throttle response. Felt far better. Won't run the CTR on anythiong but Optimax.
I have it on good authority that on inspecting and rebuilding engines up at the TVR factory it has been noted that those motors that have been run on Optimax are vastly cleaner when taken apart with no residue buildup compared to those run on the usual crud.
I found Safeways UL apalling. Made my car run like a dog (a fat old dog rather than a whippet)
Roop
I have it on good authority that on inspecting and rebuilding engines up at the TVR factory it has been noted that those motors that have been run on Optimax are vastly cleaner when taken apart with no residue buildup compared to those run on the usual crud.
I found Safeways UL apalling. Made my car run like a dog (a fat old dog rather than a whippet)
Roop
Although there is certainly an 'I've paid for it so it must work' effect, it does seem to do something. It's very high detergent content will clean the injectors which should help the car run a bit smoother, but the high octane won't make a blind bit of difference unless the car's mapped for it.
Whilst your technically correct - any modern car worth its salt with a knock sensor will have 98RON set as it's default and then retard the ignition - i.e. it run's in "constant" correction mode when you are on standard.
spnracing said:Many modern cars have knock sensors to detect lower octane fuel and back off the timing but not the other way round.
If you have a knock sensor there is little point in setting the car to be "normal" at 95RON - given the knock sensor is there (if you see what I mean)
Even my lowly X5 is set at 98RON as the normal setting - hence bunging in SUL or Optimax does noticeably increase the performance.
J
Interesting about the detergent. I can't say I noticed a power difference, but the pinking stopped on Optimax, and oddly remained quiet on the subsequent tank of 95. The only theory that fits is that Optimax cleans out carbon etc from the combustion chamber. Now I normally run 97, and if the pinking returns I'll use one tank of Optimax to clean it up.
Not cos I'm tight (although I am :-) ) but because I "can be sure" that Shell is up to no good.
Not cos I'm tight (although I am :-) ) but because I "can be sure" that Shell is up to no good.
joust said:Even my lowly X5 is set at 98RON as the normal setting - hence bunging in SUL or Optimax does noticeably increase the performance
Not if it's a standard UK market car it's not (according to the workshop manual-incidently if anyone needs this I have it on DVD-Rom) 95 RON is the setting unless you have the dealership download the alternate map.
On the topic of Optimax, I hear that it has a limited 'shelf life' meaning that it loses it's higher octane rating the longer it's stored.
Fill the tank and use it all with a couple of drives and it's fine, but if you use your car occasionally you may well find a differing performance..
I don't know this for sure, just heard it a couple of times elsewhere.
Minghis.
Fill the tank and use it all with a couple of drives and it's fine, but if you use your car occasionally you may well find a differing performance..
I don't know this for sure, just heard it a couple of times elsewhere.
Minghis.
Mines an import - and hence states in the manual (and actually has it written on the flap) that 98RON is the default - trust me it makes a large difference on mine!
jaydee said:
joust said:Even my lowly X5 is set at 98RON as the normal setting - hence bunging in SUL or Optimax does noticeably increase the performance
Not if it's a standard UK market car it's not (according to the workshop manual-incidently if anyone needs this I have it on DVD-Rom) 95 RON is the setting unless you have the dealership download the alternate map.
Mind you.... why on earth would you pay UK prices for X5's and wait 12 months
J
jaydee said:Nice car, but not at UK prices IMHO (particularly up against the cayenne and the toerag). I bet that makes a great deal of a difference, it certainly does on the M5.
It'll be interesting to see what I plump for when it comes up for changing time in 1.5 years - so much choice.....
I still think the X5 looks the nicest of them all - and could I actually drive around in a £45k VW??????
J
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