An interesting document on fuel, Optimax and octane boosters. Might explain why the 2001 car I tried before going for a 02 one felt a bit less eager and even a bit underpowered. Makes you wonder if it

 

Yes i use octane booster the Aldens stuff and BP Ultimate you can tell the difference the car seems to respond better.

 

Miller's octane booster is very good and I regularly use the stuff for Santa Pod (combined with Optimax). Seems to increase the engines responsiveness and give it a little edge. Usually about

 

I thought ultimate was over one hundred octane

 

Andy, if you haven't already done so, follow the link posted above - the central thrust of it is that Optimax isn't anywhere near 98.6 RON by the time it gets to your tank, and that Shell are only prepared to certify it as being 95 RON for the purposes of random Customs & Excise checks. The suggestion seems to be that once it has stood in the fuel tanks at the filling station for a while, and has then sat in your tank for a bit longer, it may not actually be much higher in octane terms than ordinary UL.

I've no idea how much substance there is to the claims, or for that matter whether BP Ultimate or any other Super UL is any different. Does make you wonder though.....

 

IIRC Ultimate is 97 point something.. I have tried it a couple of times (not through choice) and have found it no different to Optimax.

mark if what you are saying is true either we haev all been 'had' or this maybe the same with all petrol.. 95 RON also decreasing in octane level as it sits in a petrol station. Its probably all relative.

I have heard this before, especially if it is left in your own petrol tank for too long, not usually an issue with the S unless you are good weather weekend driver.

 

At the Midlands Meet I got caught short and half filled my tank with fuel from a JET garage. To my mind the car seemed a damn sight more responsive than with Optimax! Don't have a JET garage locally so cannot experiment!

 

this is why if I want ultimate 'go' I use Q8 98ron but it's expensive

was looking at my demon tweeks catalogue last night thinking about Millers Octane booster

 

I have recently mixed Ultimate and Optimax and noticed a big difference.... I wonder if using the same fuel for a while makes the car not react as welL

 

If you follow some of the other articles referenced in that link one guy did some bench tests on a few fuels and some of the standard ones were as good as the octane boosted versions. I use optimax more because of the improved detergents and additives over other fuels out there just now but seems like the octane level isn't as high as it says on the tin. Most cars take over 100 miles for the engine sensors to fully adapt to changes in fuel so if you fill up one tank full you probably won't see much instant difference upping the RON value though downgrading to standard 95RON can make a noticeable difference if you've been running on higher RON fuel.

Octane boosters can leave deposits as shown in some of those articles too so i'll just be usung standard optimax for now.