Since recently carrying out an oil and filter change on my 2003 wrx i have noticed that the engine has developed a tappety rattle.
I used millers cfs 5w 40 as subaru recommend a 5w for new age imprezas but i am wondering if i should have used a 10w.
The dilema should i drain out the oil and replace with a 10w 50 or is it safe to carry on until the next oil change in about Feb?

 

shouldnt make it tappety

 

funny thing.i did exactly the same with millers fully synthetic 5/40 oil,and my wrx 2005 is tapping when hot.it is the lifters making the noise.before i changed the oil it was not tapping.i will be going for 10/40 fully synthetic next time,as the lifters don,t like the thinner oil.