So I consider myself lucky, I have 120K miles on the old 2014 ecoscrew... if the temp drops and I leave the car more than 24 hours without a start, it will give a quick 2 second rattle sound, but very very minor.

I actually had a "tune-up" where they re-ran the calibration and did DTC checks and stuff and said it was well within parameter.

On cold days, I will prime the oil pressure by stepping on the throttle for maybe 10 seconds before letting it turn over.

Should I wait until I actually get a code or should I pre-emptively just do the work?

I've also have been using FL500S filter and using Mobile 1 since day 1 (even Mobile 1 extended) and changing every 4000 miles

I also have done the drill mod to keep the moisture out and other crap as I don't have a catch can.

 

Most likely this. My 2011 had this problem. My extended warranty covered it. Not sure how much it cost. I think it had something to do with timing chain tensioners.

 

The rattle is caused by excess length in the timing chain due to "stretch" - each of the links wear enough on a chain that's so long that you get slap, so yes it's serious and recommended to fix if it happens every time.

The new GF6 spec oil was made primarily to combat this excessive wear on timing chains, the industry spec actually uses an ecoboost engine for standards testing/certification, nearly all the major oil brands should be at that spec now, but it's so very important to change oil often, going anywhere near the 10k OCI is just such a bad idea that doesn't work in reality, especially so on the EB engines.

Mobil1 is a good oil, but i've never had luck with it, it's always made any engine i put it in, rattle, so i never use it, ever. Changing often is way more of an engine protection plan than anything else, make sure you use a quality filter.

 

Not pulling a code and only get the rattle if I leave the truck in the cold > 2-3 days, but that said it will obviously get worse. Guess I'll have to budget.

I would almost have no problems with a non-DI modern truck motor using a high quality Group IV/V oil with a good filter >6000 miles... say a older Coyote BUT with the DI, fuel dilution, you really just can't.

My 2012 Volvo V70 T5 suprpringly has an oil filter close to double the size of the FL500S and uses close to actual 7 quarts of Group 5 synthetic (recommended Euro Castro Syntec or Motol) - and even Volvo still recommends 5000 miles
Its a low pressure turbo, not super high strung 5 cylinder with traditional injectors

 

I know the EB often has a bigger problem, but...