450's don't have an adjustable oiler, as you've found. The oiler is a bit stingy, but it's the same set up that has been used for years on other models like the 340/345 up to several of the new 400 series saws. Simple, but it works in most cases. The problem you are running into is that the 450 "rancher" comes with a 20" bar that the oil pump can't always keep up with. Especially with some woods like ash. Even a slightly dull chain starts to build up heat.
That SKU was created for Lowes to be able to sell a saw at a $399 price point when the cost of the 455 would no longer allow that. The "solution" was to stick an 80DL 20" bar on the 450 and write "rancher" on it. I sell plenty of 450's with 18's on them, but won't sell one with a 20.