Using Shell optimax
Discussion
Hi,
Id be very interested of hearing about your experiences with shell optimax. any porsche make, cayenne owners in particular.
When I first got the car, was running it on Sainsbury’s stuff at 78p a litre and didn’t really consider how well it ran etc. Then I filled up one tank on optimax and ran the car as normal – that seemed fine too. When I needed to refuel the other day I put sainsburys stuff back in the felt awful – really sluggish, really slow, needed to kickdown constantly to get any response from it. It was pretty hot that day so I put it down to the climate being on but somehow I don’t think that would matter so much.
Just wondered if anyone had any similar experiences with optimax? Do you use it? Do you notice any significant differences in it? Is it worth the extra price – do you get any better fuel economy from it? Is it worth it?
I phoned my mate at the OPC who checked with servicing and they said optimax is the best thing for it!
Look forward to your comments
Id be very interested of hearing about your experiences with shell optimax. any porsche make, cayenne owners in particular.
When I first got the car, was running it on Sainsbury’s stuff at 78p a litre and didn’t really consider how well it ran etc. Then I filled up one tank on optimax and ran the car as normal – that seemed fine too. When I needed to refuel the other day I put sainsburys stuff back in the felt awful – really sluggish, really slow, needed to kickdown constantly to get any response from it. It was pretty hot that day so I put it down to the climate being on but somehow I don’t think that would matter so much.
Just wondered if anyone had any similar experiences with optimax? Do you use it? Do you notice any significant differences in it? Is it worth the extra price – do you get any better fuel economy from it? Is it worth it?
I phoned my mate at the OPC who checked with servicing and they said optimax is the best thing for it!
Look forward to your comments
hi, sorry i dont have a porsche.
i used to be cynical about all claims for special petrol allied to premium prices.
however, when a magazine tested optimax clean engine claims on an identical model to my (then) car, i was interested. they used an endoscope to photograph the inside of the cylinders, then did 3000 miles on nothing but otptimax. the bores went from black to shiny metal coloured.
well i was converted, and used it in my "performance" cars ever since.
i used to be cynical about all claims for special petrol allied to premium prices.
however, when a magazine tested optimax clean engine claims on an identical model to my (then) car, i was interested. they used an endoscope to photograph the inside of the cylinders, then did 3000 miles on nothing but otptimax. the bores went from black to shiny metal coloured.
well i was converted, and used it in my "performance" cars ever since.
deeen said:
hi, sorry i dont have a porsche.
i used to be cynical about all claims for special petrol allied to premium prices.
however, when a magazine tested optimax clean engine claims on an identical model to my (then) car, i was interested. they used an endoscope to photograph the inside of the cylinders, then did 3000 miles on nothing but otptimax. the bores went from black to shiny metal coloured.
well i was converted, and used it in my "performance" cars ever since.
I saw something like that in Evo once ages ago. They used Optimax in 3 cars, one was a fast Jag I remember and one was a Honda I think. I remember the photos from the endoscope. It certainly seemed to clean the engine.
What I remember more clearly were the significantly improved acceleration times for all the vehicles they put Optimax in.
raftom said:
Never tried Optimax before but last week I put BP Ultimate (100 octane’s) for the first time and my jaw dropped. What a difference.
It was noticeable just as I was leaving the fuel station. More responsive, less lag and the car felt much better overall.
Definitely thumbs up.
Is this stuff a genuine 100 octane? i am obviously mistaken, but I thought i read somewhere that it was 98.5 like optimax only more expensive.
Yep, I think the BP stuff is guaranteed to be a minimum of 98 octane - certainly nothing about it being 100.
I would have thought that ECU settings determine the appropriate fuel to use - i.e. an ECU mapped to run on 95 Octane and with knock sensor matching this will not give any better performance on 98 RON fuel (but I could be too simplistic in my reasoning)
I would have thought that ECU settings determine the appropriate fuel to use - i.e. an ECU mapped to run on 95 Octane and with knock sensor matching this will not give any better performance on 98 RON fuel (but I could be too simplistic in my reasoning)
clubsport said:BP Ultimate in the UK is the same as the old BP Super Unleaded: 97 RON.
Never tried Optimax before but last week I put BP Ultimate (100 octane’s) for the first time and my jaw dropped. What a difference.
It was noticeable just as I was leaving the fuel station. More responsive, less lag and the car felt much better overall.
Definitely thumbs up.
In other territories it may have a higher rating (just like Optimax does outside the UK).
As has been pointed out by those in the trade, most of the petrol in this country comes from the same tanks at the refinery - some brands may add octane boosters or additives in the tanker.
My local Shell station is closed for several weeks while the underground tanks are replaced, so I've had to use BP Ultimate just recently. It's a fairly hefty 89.9p a litre and to be honest seems no different to regular unleaded. At least with Optimax I do get marginally better economy. Not enough in percentage terms to justify the price premium alone though.
clubsport said:
Never tried Optimax before but last week I put BP Ultimate (100 octane’s) for the first time and my jaw dropped. What a difference.
It was noticeable just as I was leaving the fuel station. More responsive, less lag and the car felt much better overall.
Definitely thumbs up.
Is this stuff a genuine 100 octane? i am obviously mistaken, but I thought i read somewhere that it was 98.5 like optimax only more expensive.
I have no idea. It’s just what says in the can around here. But the difference to the normal 98 (which they no longer sell) was surprising. Will try Optimax too to see how it goes.
Maybe someone here could enlighten us all about the inner depths of the octane world.
rubystone said:
I would have thought that ECU settings determine the appropriate fuel to use - i.e. an ECU mapped to run on 95 Octane and with knock sensor matching this will not give any better performance on 98 RON fuel (but I could be too simplistic in my reasoning)
That as some logic. I tried some googling and came out with this (www.repairfaq.org/filipg/AUTO/F_Gasoline6.html ):
repairfaq said:
Can higher octane fuels give me more power?
On modern engines with sophisticated engine management systems, the engine can operate efficiently on fuels of a wider range of octane rating, but there remains an optimum octane for the engine under specific driving conditions. Older cars without such systems are more restricted in their choice of fuel, as the engine can not automatically adjust to accommodate lower octane fuel. Because knock is so destructive, owners of older cars must use fuel that will not knock under the most demanding conditions they encounter, and must continue to use that fuel, even if they only occasionally require the octane.
If you are already using the proper octane fuel, you will not obtain more power from higher octane fuels. The engine will be already operating at optimum settings, and a higher octane should have no effect on the management system. Your driveability and fuel economy will remain the same. The higher octane fuel costs more, so you are just throwing money away. If you are already using a fuel with an octane rating slightly below the optimum, then using a higher octane fuel will cause the engine management system to move to the optimum settings, possibly resulting in both increased power and improved fuel economy. You may be able to change octanes between seasons ( reduce octane in winter ) to obtain the most cost-effective fuel without loss of driveability.
Once you have identified the fuel that keeps the engine at optimum settings, there is no advantage in moving to an even higher octane fuel. The manufacturer's recommendation is conservative, so you may be able to carefully reduce the fuel octane. The penalty for getting it badly wrong, and not realising that you have, could be expensive engine damage.
In 944 turbos the base recommendation is 95 RON, so maybe the ECU can be optimized to 98?
Any ECU experts to comment?
It isn't only to do with the octane rating but also the type of engine that it's being used on and how good the knock sensing is and the mapping strategy employed.
First of all, octane ratings aren't comparable the world over, the USA uses MON+RON/2 and we use RON I believe. 92 octane MON+RON/2 is approximately equivalent to our 95 RON stuff over here- but it's more complicated then that really.
When an engine is developed, and is put on the dyno for mapping , when you sweep ignition with torque at a particular speed at Wide open throttle (WOT) you'll get what I call an "ignition loop" ( think of it as a two axis graph with ignition along the X axis and torque along the Y axis). At some engine speeds this loop is very steep- so a few degrees change of ignition will make a big difference in torque. On top of this some engines inherently have steeper ignition loops everywhere.
Engines with steep ignition loops are ones that typically have a high compression ratio specified as standard and engines that breath well, like, for example the BMW M3 or the Porsche 996 GT3s. Engines with VCT will have steep ignition loops even at low engine speeds. And boosted engines have savagely steep ignition loops! This means that provided the knock system is any good, if you change octane to a higher rating engines with steep ignition loops can benefit a great deal.
The knock system must be calibrated such that it can take advantage of the new octane rating also. I'd say modern Porsches -993 onwards CAN. This involved a system that actively goes INTO knock and then retards actively continually. Where an engine is NOT knock limited- such as at peak power you'll gain no torque at all.
I'd say the most to benefit these days from higher octane fuel would be boosted cars, like the 996 TT, but the benefit isn't linear: you might gain, say, 4 Nm of torque at 4000 rpm going from 95 octane to 98 octane but then going to 100 octane may gain nothing at all.
Most naturally aspirated engines (non turbo charged) will benefit from higher octane more at low speeds and mid range with very little if anything at top end- because they're rarely knocked limited there.
First of all, octane ratings aren't comparable the world over, the USA uses MON+RON/2 and we use RON I believe. 92 octane MON+RON/2 is approximately equivalent to our 95 RON stuff over here- but it's more complicated then that really.
When an engine is developed, and is put on the dyno for mapping , when you sweep ignition with torque at a particular speed at Wide open throttle (WOT) you'll get what I call an "ignition loop" ( think of it as a two axis graph with ignition along the X axis and torque along the Y axis). At some engine speeds this loop is very steep- so a few degrees change of ignition will make a big difference in torque. On top of this some engines inherently have steeper ignition loops everywhere.
Engines with steep ignition loops are ones that typically have a high compression ratio specified as standard and engines that breath well, like, for example the BMW M3 or the Porsche 996 GT3s. Engines with VCT will have steep ignition loops even at low engine speeds. And boosted engines have savagely steep ignition loops! This means that provided the knock system is any good, if you change octane to a higher rating engines with steep ignition loops can benefit a great deal.
The knock system must be calibrated such that it can take advantage of the new octane rating also. I'd say modern Porsches -993 onwards CAN. This involved a system that actively goes INTO knock and then retards actively continually. Where an engine is NOT knock limited- such as at peak power you'll gain no torque at all.
I'd say the most to benefit these days from higher octane fuel would be boosted cars, like the 996 TT, but the benefit isn't linear: you might gain, say, 4 Nm of torque at 4000 rpm going from 95 octane to 98 octane but then going to 100 octane may gain nothing at all.
Most naturally aspirated engines (non turbo charged) will benefit from higher octane more at low speeds and mid range with very little if anything at top end- because they're rarely knocked limited there.
raftom said:
In 944 turbos the base recommendation is 95 RON, so maybe the ECU can be optimized to 98?
Any ECU experts to comment?
The 944 Turbo Compression Ratio is relatively low by modern standards, so if you were to switch to a New more up to date ECU system with decent wide band knock sensors and you reoptimised both the ignition and boost I'm quite confident you could make signicant gains in torque throughout the rev range.
I would definately recommend Optimax. I'vr tried other superunleaded fuels which are 97 octane but I find throttle response much crisper using Optimax with the added bonus of good fuel consumption.
The BP equivalent of Optimax is also supposed to offer a similar combination of good performance/economy but I haven't tried it yey.
Geoff
The BP equivalent of Optimax is also supposed to offer a similar combination of good performance/economy but I haven't tried it yey.
Geoff
I always use some form of Super in the TVR (Optimax if I can), I notice the power drop straight sway if I fill up with 95 unleaded.
Plus with Optimax you get the little Top Trumps type cards when you pay, telling you the spec of different performance cars and the specific tyre Michelin recommends for it!
MOD.
Plus with Optimax you get the little Top Trumps type cards when you pay, telling you the spec of different performance cars and the specific tyre Michelin recommends for it!
MOD.
frogisland said:
Loopy juice optimax everytime - definite noticeable difference in performance, consumption and wallet. Have found my consumption of fuel always increases - get 10-15% less mpg.
Used in my previous V6 406 Coupe and my present 968CS
JP
so is it a bit like the fosters v stella debate
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