“My classic Bristol 400 gearbox was filled with 50 grade oil and a loud bearing whine was apparent and the gearbox noisier than it should be (after a very expensive rebuild only about 6k miles ago). On the advice of Opie I changed to the Millers Classic Gear Oil 80W-90 GL4. The loud bearing whine was immediately greatly diminished. I am hopeful that after some miles the general noise is reduced too.”
