i serviced the car today for the first time, didnt do a coolant change as a garage is doing cambelt and waterpump next week. when under hte car putting the new oil filter in i noticed theres a pipe nipple on the underside of the expansion tank that has no pipe attached. i THINk it might be an overflow thing, but i wasnt sure. can anyone shed some light on this? oh, and andbody notice much difference running 10-40 GTX oil, thats what castrol said was right, but i thought it was a 5-30?