Seriph Hydraulic oil not only burns but does so at an extremely high temperature, sufficient for a lot of surrounding materiel to reach it's flash point very quickly. As nilnotedks has already stated, once alight it will burn fiercely and in an atomized state it will ignite very easlily. After a cabin fire a wheel well fire is the most likely to require an immediate evacuation and will then destroy your aircraft, (ask Air France and others, B747).