A friend of mine is getting rid of his old 6 point harnesses because they are too old for his rally car but seeing as they are in very good nick i thought they might do for my fury.

the problem is although they arent damaged they are fairly dirty and i dont really want to use them as they are. can they be washed? if so how (can i just stick them in the washing machine at low temp as you would with a normal synthetic fabric?)

Id suggest a gentle brush and sponge with some mild detergent. Whatever wont come out is probably there to stay.

Id definately not put them in the washing machine. Overlooking the damage youll do to the drum of your machine, you dont want to immerse the buckles and fittings for any length of time.
Remember you may one day have to entrust these with your (and passengers?) life, Id not be arsing about with them or doing anything which could potentially or otherwise damage them.

I would give them a scrub with fairy liquid and a brush.

I would imagaine they woul damage your machine if u put them in there.

a bar of vanish soap does well on this type of thing and especially oil stains

I dunked mine in a bucket of hot water and washing up liquid, then laid them out on the path and blasted them with my pressure washer.
Worked fine, but not pristine

Vanish works well as already suggested, use a nail brush. Make sure you dry them properly otherwise they go mouldy. Guess how I know.

Parachutists (who also have to clean life entrusting webbing) use the foaming upholstery type cleaners you can get which go on from a can with a brush on, and then wipe off....

Chris

Used Vanish on mine as recommended by a quilified parachute rigger.