I just used a rental from an auto parts store. I don't think there was an issue here-- I felt as though it was holding pressure reasonably well.
I did this and there was no jump in pressure. Don't know if the thermostat has to be open or not...
I haven't really noticed. Wondering if its fuel since all of my spark plugs were black! This would be a preferable issue. =)
This would make me very sad.