Valve train is getting louder

About two weeks ago I changed it to Wolfs Head Synthetic 15W40.

Should I switch it back to something organic like a Valvoline or Castro 5W30 for winter use?

Please recommend the best for this time of year (and for summer use) and 225K. Thanks!

P.S. It's a _1996 (1993 was a typo earlier. )

I would say a little bit of both, but I think more so because it got cold right after I changed it. I've used that weight of oil before, and didn't notice it as much, but that was over two years ago. (I have time before Christmas to switch it back to a lighter weight if needed.) Also, the garage it's in now where I reside is smaller, so the clicking is more noticeable.

The oil container also says it's for gas _and diesel engines, so I'm thinking the oil may not be the cause.

Both, catch up with you later 2 nite, gotta run.

Just was out running errands, got back, popped the hood and as I listened very closely in the garage with it running, yes the lifters are probably going or may be bad, but after listening closer, another clicking sound is coming from a small device to the right of the air filter, and has a few small hoses and wires coming from it, and I have no idea what it is. Not even sure what it is and will trace to where the hoses go soon. The top part of the device has a small round head and it gets more narrow towards the bottom. And the clicking sound it's making is a constant and even sounding clicking.