Is it really worth paying the extra for higher octane fuel?

 

I am not sure how the Octane numbers differ in Scotland, but here in Florida, we usually have 87,89,91,93. I always use 93...anything above that is a waste if your not running an aggressive engine remap.

 

Here in Toronto, the octane levels are 87, 89 and 91. There are only a handful of stations with 93. There is nothing higher. The car is designed to run on 91 so why pay more? Modern engine management systems restrict or increase air flow from 'normal' when the octane levels are different from 91. In the old days, air flow was constant so an increase in octane would produce changes in the engine output.
However, as in anything on these forums, there are lots of opinions. My advice: Don't bother. If in doubt, make up your own mind and try it out. If you notice a justifiable difference for the extra cost then go for it.

 

well, US and europe's octane ratings aren't quite the same for those wondering.

http://en.wikipedia.org/wiki/Octane_rating

 

Generally, octane ratings are higher in Europe than they are in North America and most other parts of the world. This is especially true when comparing the lowest available octane level in each country. In many parts of Europe, 95 RON (90-91 AKI) is the minimum available standard, with 97/98 RON being higher specification (being called Super Unleaded). The higher rating seen in Europe is an artifact of a different underlying measuring procedure. In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in Canada, the United States and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in Canada and the US, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90?91 US AKI=(R+M)/2, and deliver 98, 99 or 100 (RON) (93-94 AKI) labeled as Super Unleaded - thus regular petrol sold in much of Europe corresponds to premium sold in the United States.

this is from Wiki-thanks Turboawd

 

im lost

 

Bottom line: if the original poster is talking about octane rating of the USA, 99 is way overkill.

 

No,I'm in the UK.

 

i can't even find 93 in SoCal

99 is overkill... my cousin used to put it in his 88 mustang GT which was running 600 WHP that thing was a beast

 

once again, 99 in europe is not the same as 99 in the US. read the article above.