there's your problem. Lucas actually entraps air in the oil and air won't compress like oil will and will cause the injectors to not fire correctly.

one oil change will make a world of difference but 2 might be what it takes to run like it use to.

 

OEM filters do NOT come with a cap. You'll need to source a new cap from somewhere. Either just order one from the dealer, or maybe get a new billet one. You can get both the fuel filter and oil filter caps in billet for about $100.

Get rid of the lucas, and get rid of that WIX filter with it's own cap and I bet it goes back to the way it was.

 

Napa filters are too bad of a choice and they come with an oil cap too.

 

I wouldn't use ANY oil filter that comes with it's own cap. I wouldn't use any filter other than a motorcraft or an international. Motorcraft oil filters are less than $20. There should really be no excuse for not using one.

With that said, I used to use Amsoils synthetic oil filters too. They did NOT come with their own cap though. They were also more than $30 and claimed to be good for 15k mile intervals. I was doing oil analysis to back everything up though, and if you want to run something different I strongly recommend OA.

 

if you want all kinds of driveability and no start related issues go ahead and use aftermarket. You want your truck to fire up all the time, and not have any issues, keep it OEM Cap and motor craft filters only. Ive done too many no start concerns through the years all because of an aftermarket cap and filter.

 

Ok here's one for you guys. I just changed my oil, 15 quarts shell rotella 5w40 and a Motorcraft oil filter. I've done this hundreds of times but I'm having a rough idle on cold starts and once it's warm, no issue.
2003 6.0 169k, egr delete, new injectors, cold air intake, etc etc all the normal goodies we do to the trucks.