Optimax v Ultimate

[Dom]

Hi, has anyone done a conparison between Shell Optimax and BP's 'ultimate' fuel in the UK? My Fiesta is currently setup for Optimax and am curious to know if I should bother changing to Ultimate and getting the car setup at the dyno again. Alternatively would it be possible/useful to add additives to the Optimax even though it already comes with additives out of the pump?

[Tim Falce]

Do you notice any power difference with different brands?
I think you will find that the fuel you buy all comes out of one big tank in Purfleet

[graham bahr]

the BP fuel is only 97 octane but optimax is 98, that said my car despite producing 100 bhp/litre makes identical power on either without any adjustments required (its on full fuel and ignition management) although its very sensative to ignition timing 2 degrees either way looses 4 brake.

[REALIST]

Graham, do you know what power you get on 'standard' unleaded?

[Onlooker]

In Australia the Mobil Hi octane has the most punch.

[GTV27]

Originally posted by Onlooker
In Australia the Mobil Hi octane has the most punch.

I find the Alfa (11.5:1 static, but lots of valve overlap) runs better on Ultimate than Optimax - despite them both being 98 octane - but have not yet tried Mobil.

Onlooker, what's the basis for your claim? (not flaming, just interested)

[avsfan733]

What is access to race gas like in other countries? I know in the US its ridiculously expensive and hard to get at

[GTV27]

Originally posted by avsfan733
What is access to race gas like in other countries? I know in the US its ridiculously expensive and hard to get at

Yep, that about sums it up here too.

Used to run on Aviation fuel purchased at the airport, but that's no longer an option. Using the 98 oct premium unleaded is about as good as it gets now.

[reddy]

you could always use elf. abuout 7 more rwhp on a 2l engine ive been reliably told.

[Onlooker]

I remember the scutineers had taken fuel samples for a class that was restricted to pump fuel only,now some competitors had been using additives etc in the past but unbeknowns to everyone the specific weight of the Mobile was higher than the other fuels and thus they quizzed all those that were "offenders" as such thinking an octane booster etc had been added or Avgas added to it,when it was revealed that all those in strife were using the same fuel,(Synegy 8000 i believe), all questioning ceased.The srutineer said that it was closer to AVgas than the others had recorded and some probally had additives in other brand fuels anyway.

[Dom]

Thanks Graham, that was pretty much what I was expecting (and hoping for!). I've heard that Optimax base RON is only 95 before they add additives - if so,is it safe to add more octane booster to this to extract a bit more bang per buck before moving up to the staggeringly expensive race 'pump' fuel?

[AlexF]

They are very different fuels...

optimax is basically high octane stuff, where as BP have lost of clever additives such as friction mofifers that work with your oil!

alex

[Barny]

I use leaded fuel supposedly 100octane, but I am cannot tell the differance in power, but use it instead of a lead additive.

[terje]

The best pump or drum fuel available is at the Elf petrol station inside the Silverstone circuit, its expensive.

Looking at RON numbers is all very well but not necessarily the rating that you should be looking at. I've had a chat with several people about fuel ratings and it seems that the MON (Motor Octane) rating is as important if not more than RON, this theory is also backed up by this report I found: http://www.btinternet.com/~madmole/R...RONMONPON.html

As for Optimax, the ratings I got from the manufactures were:

Guarantee RON 98, Typical 98.6
Guarantee MON 86, Typical 87.5
Fuel Density 720-775, Typical 743 (Kg/m^3)

As BP Ultimate is a new product I haven't looked into it but I would think that it is unlikely to be much better that Optimax.

[RMR]

Dom,

i always use optimax when racing, it works fine. dont notice and difference but saves adding additives. never had a problem. last race i used BP ultimate and so did a friend. both of us blew engines. superstition now tells me to use optimax

[Dom]

Thanks everyone for your input, I think i'll stick to the devil I know - at least until something better comes along...

Terje, out of curiosity how much is the Elf stuff st Silverstone?

[RMR]

about 1.20ish a litre. its a rude price its def not less.

[terje]

Originally posted by RMR
about 1.20ish a litre. its a rude price its def not less.

....thats about right for the pump fuel although the barrel fuel is a bit more- not sure exactly. If you ring any of the fuel campanies Shell/BP their always happy to send you the spec sheet on their fuel ;o)

[JGM]

Putting fuel of a higher octane than your engine is designed for will not enable it to produce more power. The octane rating of a fuel relates to its anti-knock or anti-detonation characteristics. Using a very high octane fuel will only deliver extra power if used in conjunction with a very high compression ratio which would not tolerate a lower octane fuel.

[CFD-9]

Yes, but on a modern engine with a knock sensor where the ECU is retarding the ignition, a higher octane fuel will allow the ignition to advance and so allow the engine to produce more power...

[Richy_Rich]

I was talking to a guy who works for Ford, part of his lab's responsibilities is to test pump fuel from random forecourts.

Apparently, BP has the most consistent RON/contents etc. All the others are 'all over the place' (his words) including shell.

This wasn't specifically about optimax/ultimate but I imagine they're included too.