I need to change the fluid in my 85 SD. Does anyone know the capacity? Is it worth putting synthetic in at 240,000? Are there any while I'm in theres to do?

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.