heating problem

i have a 92 euro 3.4 dual twin cam......the engine only heats up when im not moving fast like in traffic...or when i dont move for a while...when im driving normaly it doesnt heat up(probly cuz of wind).. i dont know why,..... im not loosing any coolant....when it heats up my fan doesnt work until its too late.(when heat light is on)..then it cools down to a certain temperature and my fan stops...to go back on a couple secondes later cuz the heat light is on again....i have two fans and ive only seen one work lol..could this be the problem....the fan that works only starts when its already two late (like a secondary fan)......

and another problem im having is when i start my car for the first time of the day it has like a rattling sound like a diesel or somthing...and my oil gauge kpa's is like at 300 or 400 (like im driving at 60mph) for about 20 mins and then the oil pressur comme's down and the rattling sound goes down too...help me!! please!:confused:

what oil should i put in it 5/30 .10/30 15/30??????

btw sorry for my bad english:silly2:

up:bandit: