I can't get Optimax so have to use Esso super 97 ron. Now the BP garage has Ultimate, which is also 97 ron. Is there any difference between the two fuels and if so, which is best for the Subaru?

thanks

JBL

 

Mine runs like a gem on BP Ultimate. Better throttle response, more torque low down, better MPG (just seen 32mpg unspirited tootle through the countryside).

Optimax is highly rated on SN and is supposed to be 98 RON. personally I don't use it because it buggered up my Morris Marina 1.7 in the 80's. (Formula Shell that is not Optimax)

 

even the same rated fuel in the same garage can be different.

97 would be the RON value, research octane number, it's ability to resist knock under controlled conditions.

However for turbo cars we'd be more interested in MON value, Motor octane number, in which the test conditions are much more appropriate to actual running conditions.

two fuels can have the same ron and different mon values.

So the moral of the story would be 'just pick the one you think your car runs best on'

I find first thing in the morning cold starts are best to feel how the engine is running.

Hope my random gibber's not bored you.

Dave.

 

Thanks Dave, quite interesting .

Does the MON value actually exist as it's something I 've never heard of or read about or are you having me on--not April 1st is it ?????

Thanks

JBL (with a smile)

 

He's not pulling your leg just do a Google search for "octane mon", and all will become clear.

 

I'm running MY00 UK Turbo on Esso super unleaded... and it seems fine to me... I've never put anything else init... But I've just relised theres a Shell garage quite local to me... So question being now... Sod the cost... But will it benifit my car if I start running it on Optimax... Will it start messin' with stuff and affect the running due to a change...
What should I do... try Optimax or stick with Esso super unleaded??? Cause it runs spot on with Esso's petrol... but then again, I've never run it on owt else... so I wouldn't know... only having owned the car for 6 months...

 

Scoobyslammed, why not just run a few tanks of optimax to see if you think it runs better.

JBL, just to confuse matters further there is another one too, pump octane number But don't worry about that, it's only for americans