I've got a factory EFI 5.0L windsor V8 in my Ford Falcon (I live in Australia). It's the same engine as in early 90's Mustangs correct? Ford Australia doesn't change the motor, they just shipped them in and slotted them into the cars, same heads, same internals, same everything except the exhaust headers. Anyway, in Australia, they recommend that they be run with a 20W50 grade oil, but it is my understanding that mustangs with the same engine are supposed to run 10W30 viscosity oil. Is this correct?