what fuel should i be using?

[the_GTI_new_guy]

Bought my mk2 16V 1991 golf with fuel in the tank. Havent filled it up yet but have read on these forums you need use optimax or equivalent. What happens if i put 95 ron fuel in, will i find a problem. Is it safe to try the normal fuel (say £10 worth) and if i get a problem top up with optimax? Cheers

[jettaTx]

I tey to always use optimax if possible as there is a noticable increase as it runs smoother and faster on the whole. Its all down to the driver but i put say 90 % optimax in mine just when i get stuck and on the red with nowhere to get optimax

[Organisys]

98 RON petrol is the recommended fuel. the RON number is a measure of how well a petrol can withstand combustion without ignition. (pre-ignition due to compression is sometimes called knocking or pinking). The ignition timing was setup by VW to use 98 RON (See owners manual or sticker inside fuel flap)

Using a lesser petrol will give you slightly reduced power and economy.

http://en.wikipedia.org/wiki/Engine_knocking
http://en.wikipedia.org/wiki/Gasoline#Octane_rating

Optimax also has detergents which help to keep fuel system clean, plus it is also VERY low sulpher, which helps prevent sulpher deposits blocking injectors etc.
http://en.wikipedia.org/wiki/Optimax

...I work in the petrochemical industry !

[the_GTI_new_guy]

I always wondered what the point was of having less sulphur. I just assumed it was to reduce the smell. Newbie alert  How would i know i am getting pre ignition? I would assume it would be a loss of power from the combustion slowing the piston as it travels up the cylinder instead of combusting at top of the stroke and forcing it down. (I may be wrong but it sounds likely to me) Would it produce and strange noises or jerks from the engine?

[Organisys]

knocking is characterised by a distinctive metalic series of short 'ping' sounds floor it up a hill and see if you can hear it.