Motorex Racing Fork Oil (SAE 4wt) 1 Litre (12 Per Box) The MOTOREX Racing Lab has now developed an additional RACING FORK OIL for the advanced forks built by WP Performance Systems which require a 4W viscosity as specified by the manufacturer. Fully complying with the specific demands indicated by the WP forks. This high-tech oil contributes to realise their full potential.