My garage floor shows every so often I have a drop of oil from the differential/rear end. Not sure how much oil I've lost over the years and thought this would be a good time to look into either adding oil or draining it and replacing.
The Austin Healey Drivers Handbook says every 6,000 miles, check the oil level and replenish if necessary.
When should the rear axle oil be drained and refilled?
Handbook says, "Use only Hypoid oil in the rear axle".
Handbook recommended Lubricants: Duckham's Hypoid 90, Castrol Hypoy, Sternol Ambroleum E.P. 90, Mobilube G.X.90, Esso Gear Oil G.P. 90, Filtrate Hypoid Gear 90, BP gear oil S.A.E. 90 E.P. , Shell Spirax 90 E.p.
Research found Healey Surgeons recommends, "Use 80W/90 EP Gear Oil". They don't mention a brand.
Moss sells, Dynolite SAE 90 GL4 Gear Oil.
This tread:
Hypoid 90/140, API GL5 or better.
Gulf EP Gear Oil 80/90/140
To recap.
When to do a fluid change?
What brand/weight of GL4 oil do most people use?
Seems a single grade 90 is recommended by the Austin Healey Handbook. (what's the advantage of multi-grade?)
Thank you.