In the past week or so truck (82,000 miles) developed a knocking noise (that I think is associated with a bad lifter). I had a mechanic listen and he confirmed that's likely what it is. Could I run synthetic oil to help the issue? It does seem to be louder when it's cold, and even then I can't hear it in the cab while I'm driving. I might do an oil change with a bottle of seafoam and see if it helps. I may end up taking it in either way, but I wanted to know if you had any advice.
A bad lifter will not make a knocking noise. It will make a tapping noise. I would recommend having a qualified mechanic listen to the noise to see if it is a lifter noise, a piston rod, or main bearing noise.
I suggest running synthetic oil either way and sticking to the recommended oil weights. Once the noise is located then a repair attempt can be made. If it is a lifter sticking then you can try the engine flush before the next oil change to see if it helps. Feel free to reach out to a qualified mechanic to help you with these checks, they will be able to properly pinpoint and fix the noise you're hearing.
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