Originally Posted By: i6pwr
My GM 4.2 w/ 160K has been fed a healthy diet of M1 with maybe 5-6 changes of non M1. Generally when it's cold outside, I will get a lifter tick or whatever is under the valve cover...never had my face in there so I cannot accurately make a guess.
The tick will last for maybe 5 sec or up to 20 sec at times....generally 5-10 sec. This is not a piston slap for sure, it will tick them abruptly stop.
Last change was Mobil 1 High Mileage and I added about 3/4 qt of MMO. I just drained it at 2K and refilled with Pennzoil Conventional and looking for a good additive but with many avail I wanted to get some opinions.
Engine runs great, very quiet when warm and the needle is steady under a vacuum gauge. May be a small amount of varnish...not sure but after this I will perform a used oil analysis and go from there.
I'd give a qt of MMO a shot for a 3,000-4,000 mile OCI, or add a pint of Kreen for the last 1000 miles of the next OCI. If its dirt, odds are you'll clean it up. If a lifter/lifters are bad, or the cam is worn nothing is going to help. I doubt its that or you'd have the tick all the time. Make sure its not an injector tick, they make noise too.