Shell Optimax

[No Nuts]

Tootling round the local petrol stations in search of Super Unleaded last night made me aware of Shell's new Optimax.

 

I called the Shell helpline and they advise it is a 98RON replacement for their Super Unleaded (which I understand from other topics here is 97RON). It's ULS too.

 

I've been running normal unleaded in my 2001 Academy car (bog standard 1.6K) all season but have been prsuaded of the safety of moving to a higher octane.

 

Does anyone have any comments on Optimax?

 

Thanks

Guy

 

 

NN blush.gif

[Dave M]

We've had Optimax in Oz for over a year now. It is used by most high performance cars and race cars that are regulated to use "pump fuel". I use in in my Toyota 4AGE powered PRB and V8 Holden. It seems to make a difference.

 

Dave

PRB87

[Jan T]

The 'Useful Information' section in my owners handbook states Unleaded 95 Ron for all engine specifications listed except for the R500 (98). Is this not correct?

Jan

 

 

[CHRIS CLARK]

Jan T.

 

Depends on which month you got your handbook !!!!!!!!!!!!!!!!

[Jan T]

Sevening.....art or science? Discuss!

Jan

 

 

[Michael Peterson]

Neither Jan, It's a passion!

[eric]

Hi

 

In france, we have not 97 unleaded but only 95 and 98 unleaded.

The 95 can be used with Caterham (in fact Aldon 103 FXS UL) distributor, but it run perfectly with 98.

If you have an Aldon 103 FXS or a Lucas, use the 98.

 

To answer to your question to use an increased octane level is never bad. So you can put without any problem 98 instead of 97 in your car, you will may be feel an improvement in hard use condition.

In France, 95 is often as regular (lower quality) and 98 is super.

 

For best cars, as Porsche, Ferrari and so on 98 is recommanded

 

[Peter Carmichael]

Unless the engine is tuned to take advantage of the higher octane, the only benefit is a larger safety margin to the onset of knocking. Under track use, the heat retained in the cylinder head may cause hot spots and prematurely ignite a marginal mixture. A high octane fuel will avoid this.

 

High octane fuels generally have a slower burn rate and lower calorific value. An engine tuned for a faster burning fuel may well perform less well (produce less power) with a higher octane fuel.

 

[philwaters]

Any comments from Roger King? Can we use it in any of the se7en engines, x/flow/k/VX/Zetec? or is it suited to the newer K's more etc etc..?

I am always wary of fuel companies claims so wouldn't mind a bit of guidence.

 

Phil Waters

The car in front must be less in control teeth.gif

[EFA]

An engine with closed loop injection should advance the ignition to take advantage of the higher octane until the knock sensor detects the advance is too great.

 

Disconnection of battery on Rover Mems (I belive) clears all historic timing data and the car runs from a default map initially then builds a new one based upon outputy of oxygen/lambda and knock sensor data.

 

Race engines such as mine and probably Peters and maybe the R500 have static timing maps. These would require re-dynoing to get the octane/timing settings 100% accurate. All of these engines should have quite a significant margin of safety in the maps though to prevent detonation on long high rpm runs such as circuit straights, so advancing the timing a couple of degrees overall (by re-programming the position of the crank sensor) might not do any harm if you are sure you will only run 98octane fuel. Its a risky business though.....

 

 

 

Fat Arn

The NOW PROVEN R500 Eaterid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

[Chelspeed]

Arnie - Aren't you confusing closed loop fuel with closed loop ignition?

 

If you have a lambda sensor then you can have closed loop fuelling, the engine will adjust fuel pulse length to get optimum lambda reading (based on a target lambda map) for that revs and throttle site. The MBE 941 has that facility and it is working on my engine.

 

If you have a knock sensor then you can have closed loop ignition, the engine advances timing until it detect knock and then retards it a knadgers. As far as I'm aware none of the MBE boxes have this facility. Do the R500's have a knock sensor?

 

Incidentally I see that some of the MoTeC boxes have the facility to adjust advance individually per cylinder. How do they do this? Presumably they have a knock sensor per pot?

[Roger King]

On the face of it there can be no harm in running this new fuel provided your engine is OK with unleaded fuel. As others have said, an engine that is set up for 95 octane fuel will not really show any performance benefit, but there is the advantage of a bigger safety margin to detonation damage under strenuous conditions (track days, etc).

 

Engines with knock sensors are often set up for high octane fuel and then automatically compensate for lower octane fuel by adjusting the ignition settings. These engines should see a small performance increase.

 

Somewhere in the back of my mind is the memory of 'Formula Shell', which was a new fuel introduced about 15 years ago. I believe that Shell ended up paying compensation for engine damage to some police forces (allegedly). I rather doubt they'll risk a repeat of that.

 

 

[millsn]

In CCC recently they put an article that describes the new fuel. Apparently one of its main properties is that it cleans the valves up thus allowing better breathing (that's aside from the octane).

 

doesn't seem cheap though.

 

Nigel Mills - 2.0 Zetec carbs

[Rob Walker]

Arnie, AFAIK there is no knock sensor used on the MEMS equiped K series engines.

[PACR]

In my 1300 x-flow (not in a seven) the Optimax seems to have made starting easier - less choke and fewer chugs before bursting into life, than the LRP I had in before. I need to run an additive in it as well, not keen on LRP as I've never heard anything good about it - apart from if you need 97 octane and there's no Super around (and you haven't got a cat). Thinking of using Castrol Valvemaster.... Anyone heard any scary stories about it? Local halfords hasn't got any in (only got Valvemaster plus which ups octane by 2 or 3 points. I think 100 + octane might be a bit silly). The Optimax is supposed to be a faster burning fuel - according to leaflet from petrol station.

 

Piers

[dhague]

I filled up from empty with Optimax yesterday, and went for a blat. Response seemed to be a bit smoother initially, although this tailed off slightly towards the end of the run - probably washing some valve crud into the bores. Also, the hot engine didn't run on quite as much when I switched off. So, it seems OK, and I do like the safety factor - my engine tends to overheat in slow/stationary traffic, so avoiding knock might be an issue as temperatures rise. This is all on a bog standard 1.6K SS, BTW.

 

- Darren

[JKJ]

PACR

 

I have been using Castrol Valvemaster +, although I didn't realise there was a lower grade, in my X-flow and I must confess the thing does seem to run alot better. Seems to start and tickover better and run with more go. There again might just be me trying to justify the cost of the stuff.