EP Gear Oils, GL4 (EP 80W90, EP 140): GL4 is the first serious level of extreme pressure (EP) performance and is specified for many gearboxes and final drives from mid 1930’s onwards.  The EP additives are for bevel and lightly loaded hypoid gears.  These EP gear oils exceeding API GL4 are idea for classic transmissions and axles requiring GL4 performance which is also suitable for brass and bronze components, ie. non-stain.