Having a look through some of my paperwork and I've notice that the z has only done about 85k miles, but obviously it's 25 years old. Should bushes be replaced due to age or mileage

I think you answered your own question, there old with 85k miles on them they won't be in tip top shape.

What about changing them based on condition? I remember changing some old bushes on my last Z. When I got the old one out and compared it to the new one there was no difference!

Of course I went ahead, fitted the new part and back on the road there was also knack all difference!

If you can see/feel they are knackered fair enough, otherwise consider leaving alone unless you have time and money to burn. I need to change my tension rod bushes and rear drop links, but I can clearly see these are leaking/split.

I didn't think 85k was too bad, think the car has been garaged most of its life

I think age is more a factor really, all rubber and rubber compounds rot over time. The z is a heavy powerful car, so there's a lot of stress on these components. Front tension rods seem to suffer badly. It all depends what you want out the car, it will likely be safe if they look good, however will you get the most out of it? That's a different question.

what bushes are you talking about the car has lots?

I was thinking more of the subframe mounts, as things like tension rods will be replaced at some point anyway

Get them all replaced with poly bushes if your doing it and they'll likely outlive the rest of the car.

I have done my whole rear end so far every bush I have to say the bushes were all in very good order for there age if you was doing the lot it would make sence to refurb the whole sub frame at the same time like I did. the whole job it a bitch to do

I have done my whole rear end so far every bush I have to say the bushes were all in very good order for there age if you was doing the lot it would make sence to refurb the whole sub frame at the same time like I did. the whole job it a bitch to do

 

In the process of doing mine mate, I've got jaffas old rear end which is already polybushed and solid mounts etc which really reduces labour. Just stripping it down to power cost the frame carrier etc. even that's been fiddly, deprecating the lower arm from the hub is a dick.