Welcome.
Most of this site tends to focus on wild trout streams, me included. While Oil does get the occasional wild fish, it should not be considered a wild trout fishery, and there are quite a few other wild trout options in that region.
That said, as large, stocked streams go, it's a good one, and I enjoy my trips there. Yes, the state park is stocked heavily throughout. There are good hatches, and the fish rise freely when you get a hatch. It stays cool enough for trout fairly long into the summer for a freestoner of its size, mid June at least, and many years into July. It also gets stocked again in the fall, though I'm not sure if it's the whole length or just the special regulation areas. It does have 2 special regulation areas, and they are good. But the regular ATW sections also fish well deep into the season, for reasons I'll explain below.
Yes, there is good access. There are places to park only every couple of miles, but a paved bike trail runs the length of it. It's kind of nice because the stocking truck runs the bike trail, leading to stocked spots far from vehicle access. It allows you to get away from crowds a bit, and those that do walk or bike distances from the car generally aren't the type that keep very many fish. It gets fished out a bit right by the access points but if you're willing to go a mile or so you can escape that.
