DH says he uses Sewing Machine Oil. The cream screw on ours was set and it really pulls the cream out. We were going to change it but decided to just leave it, especially as the tool to turn it didn't come with the separator we were going to have to hunt for one or get it made at the local place that does that sort of stuff.
The retired Vet up the road had one he said we could borrow that was one from a dairy, huge thing, we declined as it was just too big for us to handle. The kitchen model is just fine for us.
I found the milk after separation for cheese was too light on and the cheese wasn't to my liking, so I always use full cream milk now.
DH loves the taste of the skim milk, I don't really drink milk so it's what he likes when he drinks about six litres a week.
I know my niece from Perth last Dec (13 year old) liked the milk and thought it was still creamy which DH always says. So possibly with the cream screw moved a tad you'd get a better result.
This site has some great information on cream separators as well as dairy products, it may be of help with the amount you turn it.http://www.ilri.org/InfoServ/Webpub/Ful ... essing.htm
There's some good cheese recipes as well.