I have this rattle but only until the motor warms up a little. My question is what happens if nothing is done? Just wondering.
Thanks for any replies.

 

It gets worse and costs more to replace more parts.

Not knowing exactly what is causing the noise without actually checking it, , but do know that infrequent oil changes with the wrong oil can can produce these symptoms .
If it is what I believe it is, the longer you wait the more expensive it will get to correct.

 

There is a TSB that addresses engine noise on 2018's with the 5.0. I would consult with your dealer for further details. I believe the TSB number is 18-2354.
Sometimes a brief rattle on start up could be something as simple as an oil filter with a poorly performing ADBV which allows oil to escape the filter over time after a shutdown. The rattle would be brief and stop when the filter fills up with oil after the engine is started.

 

Thank You for the reply’s