Shell Optimax - Honest John
How are we all doing on the new 99Ron Shell Optimax? I thought there would be no point in trying it in a 2.0 litre Mondeo because Fords are set up for 95Ron premium, but I tried it all the same. Acceleration is certainly better even though economy isn't because I've been using the extra acceleration. But anyone with a German high performance car or a turbocharged SAAB or Volvo should have been seeing some serious improvements both to performance and fuel economy. Have you?

Re: Shell Optimax - Knows little about cars
Any point using it on a 1.8 Toyota Avensis ?

PS - what do you think of the new fiesta, as previewed in "another place" (*) ?

(*) Channel 4's motoring website for "Driven"
Re: Shell Optimax - Jonathan
I have been using it and am seeing a slight improvement in in performance, but an improvement of 2-3 mpg (small I know) in efficiency. My car is set for 98 RON minimum and seems to like it (Mazda 2.5 V6).

Anyone else got any horror stories?

Re: Shell Optimax - Knows little about cars
How do you know what your car is set for, RON-wise ?
Re: Shell Optimax - Jonathan
It says in the petrol flap, super bleiflei, super sans plomb, super unleaded. Min 95 RON
Re: Shell Optimax - Alwyn
In Portugal unleaded is " Sem Chumbo"

Re: Shell Optimax - richard turpin
BMW 328i. 3 thanks of it. Have not noticed anything.
GUY, how is the Golf on LPG. Do you notice it being smoother than petrol?
Re: Shell Optimax - Cymro
Should say "Di-Blwm" in Wales, Alwyn, but sadly it does not.
Re: Shell Optimax - Guy Lacey
Ahhhhh, a "German high performance car" - you must be refering to my Golf GTI HJ!

Sorry, I run it on LPG but, just for you, I'll stick in some Goldfish Juice.
Re: Shell Optimax - Richard Hall
Tried it in my Audi Coupe 20V with stunning results. Feels like an extra 20 BHP, and much smoother at low revs. Ordinary super unleaded does not make such a dramatic difference. I will be using it from now on whenever I can find it. Can't comment on fuel economy yet as I haven't been using it for long enough.
Re: Shell Optimax - Ian Walker

I tried it for 3 (full) tankfuls in my Audi 90 20V with no discernible improvement. No change in economy (31.5 mpg), no change in performance. Mild sagging feeling in wallet.

Definitely no improvement at low revs (ie less than 4k).
Re: Shell Optimax - richard turpin
Sorry, I mean tanks.
Re: Shell Optimax - Andrew Barnes
Tried it in my Golf 1.8T. I can certainly feel the difference, but economy suffered because I was using the extra poke!

Re: Shell Optimax - Roger Jones
I have been running my Golf VR6 and MB E320 Coupe on Optimax since it came out. Not quite enough data yet to discern any change in fuel consumption, but I'll report in later. I can't say that I have noticed any difference in performance, but then I drive quite gently. All a bit of a conundrum, really, but as it's now cheaper than basic unleaded was six months ago I don't mind keeping faith and continuing to buy it.
Re: Shell Optimax - Andrew Smith
It feels faster and smoother but.....about the same level of improvement as I get when I clean the car. So it could all be in the mind.
Re: Shell Optimax - Dan J
Is everyone sure this isn't the "placebo" effect? I've had a go with a few tankfuls and notice no difference whatsoever. I reckon if Shell had told everyone what they have done re Optimax, and were simply selling normal unleaded at a higher price, people would still find a difference. I am not saying they are for a moment, but you know what I mean...

Same as "these pills will alleviate headaches" in medical tests, it is amazing the number of headaches smarties can cure!
Re: Placebo - Andrew Smith
I reckon your probably right. Hence the need for a control, in this instance think how much better a car feels after you've washed and vacuumed it. Now compare this to the "improvement" felt when changing to optimax etc.

I used to like the just serviced feel that a car had, even when I had serviced it myself. Since consenting to laziness and using main dealers I get the opposite. Because I drive one of their courtesy cars which all seem to be new with less than 2k miles my car always feels like a heap in comparison.
Re: Shell Optimax - Richard Hall

What fuel were you using previously? I was running on ordinary 95 octane unleaded because super unleaded didn't produce enough of an improvement to be worthwhile. The 20V engine runs a fairly high compression ratio, and the engine management should advance the ignition timing to suit the higher octane fuel. If you have a minor fault in the engine management system (like a faulty knock sensor), the ECU may have reverted to the built-in default ignition timing setting, which is so conservative that the car will probably run on paraffin. You don't get any warning lights to tell you that this has happened. It might be worth plugging it into a diagnostic tester and checking for fault codes - you can build one yourself using the instructions at

I am definitely getting better throttle response at low revs, and a lot more power above 4000 rpm. I switched back to ordinary unleaded for a couple of tanks, which confirmed that the fuel was making the difference.
Re: Shell Optimax - Ian Walker

I was previously using BP 95 octane - again super unleaded hadn't shown any improvement.

The compression ratio is listed variously as 10.0:1 or 10.3:1. My homemade code puller has never shown a single fault on any of the Audis I've owned - all I ever get is 4-4-4-4, so I guess the knock sensors are OK. However, they're fairly easy to test, so I'll have a go at the weekend.

I was surprised at the lack of improvement with Optimax, but the engine may be getting tired at 80k miles, oil consumption is around 1 litre/2K miles. A compression test is probably in order, but I'm fairly sure that the ECU is happy.

BTW - is an excellent site, ditto

Re: Shell Optimax - Ben Chapman
I switched to Optimax from Shell Super, and notice a small improvement in performance and economy. My engine has standard compression ratio and i run standard ignition timing of 6deg. The engine now runs noticeably smoother on this fuel. I now use Optimax exclusively. Owners of old cars like mine with unmapped ignition will only yield the benefits if there distributors are adjusted to the correct settings, which may explain why some people on identical olders cars experience less differnce than others.
Whether your car will benefit from using Optimax depends on whether the ECU carries a MAP for the 98RON fuel. Some high performance cars like the Vauxhall Carlton GSi 24v will only produce a very small improvement on 98RON fuel, because the ECU has three ignition maps. None of these are set for more than 95RON. Companies like Superchips claim performance improvements from using their products, but all they have done is plagiarise Vauxhalls map and advance all the settings five degrees.
However, many cars such as Volvo 850 T5's claimed performance figures will have been achieved using 98RON fuel. These cars are mapped to run on 95RON as a minimum.

Re: Shell Optimax - Richard Blackburn
I've been using Optimax exclusively for some time (MB C240 automatic). I think there is some improvement in both performance and in MPG, though I can't say it's spectacular. I'd have to do some more thorough tests. However, like another in this thread, I tend to drive fairly gently. From the latest calculation, I've been getting 25mpg (this being a mixture of motorway (one 120 mile round trip) and short journeys (the latter totalling 160 miles or so). To be honest I don't really know if this is good or bad for this car, which is a fairly recent acquisition.

I sometimes drive a Metro 1.3, but have not tried Optimax in that as yet. It could certainly do with a hike in performance, though...

Re: Shell Optimax - ROBIN
Now we have petrol nearly as good as it was 35 years ago can we please have diesel nearly as good as it was before some halfwit decided we needed it in low-sulphur form?
Re: Shell Optimax - Andy Bairsto
I have a Z3 2.8 and it is designed to run on 91 octane putting liquid gold init makes absolute no difference
Re: Shell Optimax - Dan J
Blimey Andy, in that case the car'd probably run off paraffin! That'd save you a bit in fuel tax...
Re: Placebo - Independant Observer
Why not treat partners' cars to a few tankfulls/get them to fill yours.

And not reveal what has been bought.

Then check consumption/get performance feedback.

Ask Honest John Right column

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