On another forum I followed a thread on Supermarket Petrol Apparantly difference between the petrol is the addretives - I copied this from this thread

 

http://www.honestjohn.co.uk/forum/post/index.htm?t=6701

 

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Hi All i am a retired tanker driver 20 years with Texaco 3 years with shell 5 years with Tesco and 3 years with Safeways and worked out of the large oil terminal at Buncefield Hemel Hempstead in Hertfordshire the petrol arrives at this terminal from 3 pipe lines BP corringdon, Fina/Total Immingham, and Shell Stanlow, and all grades come down the same pipe and pumped into the companies storage tanks in there own depots each driver is given a loading card like a credit card and if a Tesco driver loads in BP the computer knows who he is and injects the correct addertive, they dont hold special tanks for third party buyers

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For normal unleaded, yes the base fuel is the same, but different additives and treat rates are used - ie. dearer petrol (Shell/Mobil/etc.) will probably have more and better additives than supermarket/cheap stations.

 

BUT......Optimax is a different beast altogether. It uses special base fuel and additive package - so no other fuel is like optimax. It's only made at Shells refinery in the North West (Stanlow) and distributed round the country. A special refinery process had to be developed to produce it. It is special, hence the price ;)

And is still cheaper than Super.

http://www.gtr.co.uk/forum/upload/showthread.php?s=&threadid=2480&highlight=octane

 

Interesting thread.

Mmmmmmmmmmm!

 

 

 

http://www.daliracing.com/v666-5/info/article_read.cfm?articleID=410

 

 

:D

What a thread!

 

So from this comment -:

 

The base for Opt is PUL, but it is treated very differently from the other fuels, taking out some of the denser compounds in the final cracker (which they tell me is only used on the opt) as the fluid moves along the process they heavy stuff is replaced with manganese which has been compounded with either Xylene or Toluene (I think the former) further additives join the party and we get opt. asked whether they understood that people are putting things like NF in their opt, the response was simple, (I am paraphrasing) 'Why bother, we don't spend millions on doing this just to get the same effect as a tin of 'off the shelf' stuff, if you want to do that then just use SUL and play games with that'

 

This would explain a lot of things I've noticed - I have an import.

Optimax does indeed prevent detonation as it would seem to act in the same way as an off the shelf octane booster.

Super Unleaded doesnt seem to reduce detonation but would give better efficiency and mpg

 

I'm gonna run some tankfuls of each through my car and make notes. It would also seem that for us Jap imports - when we change fuels we should reset our ECU's so that it learns the way the fuel burns, and not chop and change from Unleaded, Optimax and Super.

Also it seems that Middlehurst Nissan (Skyline tuners and a good garage) have noticed an increase in the number of O2 sensor failures and Optimax usage.....

 

I'm not gonna run this in my car anymore as an everyday fuel - the opinions I've read seem to suggest the cleaning properties might be harmful over time.