99 octane or 98

[WeeG]

The fuel as it leaves the depot is the same, often retailers share fuel and there are various share agreements between them. What the real difference is, is the additives added prior to sale. This is most often in the lorry on route to the pump. This is where the main differences between branded fuel and supermarket fuel is.

For a stock car, 95ron is safe. You will not be making the quoted power output, that could be between 5-15% less then the manufacturer states (can't quite remember the source of that). Just like mpg figures. Our alfa clearly states in the manual that to get the 155ps the *car* can achieve, 98ron or more is required. The wife doesn't care though.... she just likes how it looks and sounds (and that it is 'nippy'). Most wouldn't be able to notice the difference of 5% or so. 5% loss on an average car producing 100ps is still making 95ps. But up to 15% loss on 240ps is another matter....

For the sake of a few quid, i use Vpower Nitro. The garage is one the way to work (supermarkets are not) and my car is mapped.

Bottom line is that super unleaded fuel will not boost your power, it will give you what you were supposed to have in the first place.

I'm sorry but i disagree, on a tuned engine, the extra octane will allow the adaptions from the ECU to advance more timing thus making considerably more power.....

 

[mike0105]

I'm sorry but i disagree, on a tuned engine, the extra octane will allow the adaptions from the ECU to advance more timing thus making considerably more power.....

You may be right of course, but I always thought that the headline would be best case scenario. So if the car is mapped to produce 300bhp, it will produce this with the correct fuel. If you use 95ron, it will retard the timing, meaning that it may produce (for instance) 270bhp.

Of course, i could be wrong, but i assumed that output was always rated under optimal conditions.

 

[_chris_]

If the cars mapped to use 98ron. Then I would say use a minimum of that to be on the safe side. You don't want the car detting due to **** fuel.