Cherokee 89 4.0 Lifter noise

My 89 Cherokee 4.0 with 280K has started to have lifter noise on startup and until the RPM's run up, I plan on pulling the valve covers to make sure the rockers are all tight, given that I am looking for suggestions to relieve this, currently using Dino oil 20/50 weight, my first 2 thoughts are to change to synthetic oil, or to run a Marvel Mystery oil thru system and change oil. Thanks to all

I wouldn't switch to a synthetic oil, because of all of the detergents in it. It can cause more harm in an older motor. And about oil additives, I would never add anything to the oil. It can react to the chemicals in the oil and cause it to foam. Thats just my opinion. Good luck.

I also have an 89. I started to hear a tapping noise about 6 months ago. Sounded almost like a water pump or timing chain failure but at the topp of the engine. It still worked great but the noise got real annoying. I ran an engine flush through it before an oil change added my normal oil plus a bottle of lucas. It solved the issue and is running smooth. A lot of crap can add up in an engine over the years, and thats assuming that the jeep always got to operating temp before shutdown and always had regular changes(yeah right). If your not looking to go into the engine just yet, try a flush. We always add a bottle of lucas to all engines that have over 225,000km (if the customer wants), I cant prove that it works, but it hasnt done any damage either.
kim