I have just aquired a 97 evo softail that has 85000 on it .I thought Id do the right thing and change the oil and filter but not sure what to use .Most forums say the Harley 20 w 50  mineral oil is not worth the price ($43 for 4ltr ) I can get my hands on Motul 1000 20 w 50 mieral for ten bucks less what are you guys out there using

Mobil 1 V-Twin or Amsoil is the go.

How much is the bike worth to you? Is ten bucks really gonna make a difference. For the Evo you can use Penrite HPR 30. Change out your oil and filter every 4000kms and youl be fine.

I agree with Joe about changing it regularly, I change oil and filter every 5000km (its easier to remember than 4000 intervals) even when using synthetic oil.

With a bit of KMs I'd go for HPR Diesel or Penrite Enduro for the summer.
The Motul 20w50 should be good too all year.