Resurrecting an old thread...
My '02 Olds Bravada with the 4.2 just turned over 105k... about 5k miles ago the motor just starting sounding noisier and noisier.
I've used M1 since new, changing every 3k-5k miles. I've heard that M1 isn't the oil it used to be so switched to Valvoline synthetic....the engine continued to be noisy (the car lives in a climate-controlled garage), especially during startup getting quieter with higher temps - my thought was maybe piston slap.
As an experiment I bought a bottle ZDDPlus and poured it in right after my last oil change, while the engine was running. Long story short, ALL of the noise disappeared and the engine now sounds almost new again and has continued for 2k miles now.
ZDDPlus doesn't make any claims that relate to my situation, but it sure worked.... does anyone have any input on possible cause /effect?
TIA.