I am completely rebuilding a 77 280Z coupe and am replacing the front and rear struts and springs with Tokico HP gas struts and performance springs. My question is what oil to use in the outer casing. The Datsun service manual says to use Nissan genuine shock absorber oil “NISSAN GENUINE STRUT OIL” or equivalent. So what do I use in its stead.

I have used ATF for 25 years. However, I know that others on this list have used Antifreeze or Marvel Mystery Oil. Essentially you want something with a thin viscosity that will aid in heat dissipation from the strut as well as prevent corrosion in the tube.

Make sure you fill the tube with the cartridge inserted - otherwise you'll get a mess!

I use ATF as well.

Any oil will do.

Here is another discussion about it:

http://www.classiczcars.com/forums/showthread.php?42377-What-type-of-oil-fluid-do-you-put-in-the-strut-cartridge&highlight=