Lifters bleeding down

the oil does say you can add it to oil and for old dirty engines it can help clean the lifters. You can add too much, not certain its your problem but you can try it. 20w-50 is getting thick but not as much as straight 30 weight. Many used 30 straight weight oil long ago (1960's early 70's) and added M.M. oil in the winter to thin the oil out..Others change to 20 weight, even 10 weight oil for winters. M.M. was used much more in the past. If 30 weight was on sale and it was still winter, you add a quart of M.M. oil and 4 quarts of 30 weight oil. If the oil still seem too thick you added a little more of M.M. oil

With 10w-30 there isn't a need now. Muti weight oils are a "new" thing