Idler pulley on 98 Malibu making jingling sound

I have a 6 cyl. 98 Malibu with 94,000 miles that runs just
fine, except the idler pulley makes a jingling sound, and not 100% of the time. A friend told me I should lubricate
it with WD-40, being careful not to get it on the belts, and to put a rag around it to catch whatever dripped.
I followed his instructions to the letter and the noise was
gone for about a week and then came back.
Is there anything else I can use to lubricate the idler pulley with that is thicker or am I going to have to have it replaced? Thanks for any suggestions.