I use oil of crossmotorcykle shoocks.Take of the small bolt upper and fill whit a small pipe.Full.when the rear end is gumpy in late sommer i fill it again. Some losses of oil is ok.Buicks are forever.
Good for you, but I would not recommend it. Use the specified hydraulic jack oil and it will serve you well. Motorcycle fork oil it too thick and you will break the (expensive) links.
