I asked the guy I got the trainer from and he told me he didn't change the oil, then I talked with someone at a place that sells & repairs machinery- decided to guy some 40wt and try that. If it's too thick or thin, I can adjust the viscosity. It's not a Lamborghini.
I filled it and left it on the bench to make sure it doesn't leak- I'll install it and see how it works later today.