I hope I can get some good new out of this lol. So I seem a lot of oil build up so I asked the guys and the said the 4.0 is bad about sludge build up. So a lot of the guys said use the mmo and run it for awhile and it will start to clean up good. Well yesterday I was driving to work and I was at about 40 psi on my oil witch seems to be norm for these motors. Well last night I was coming home looked up and it was sitting at about 12/13 sometime back up to 35/40. I'm running the motorcraft oil filter for the 5.0 witch a lot of guys say use. So I'm not sure if I'm uncovering a problem or what so all the help would be awesome before I put money into it and it be something worse than I want thanks.

 

I've never heard of the 4.0's being sludge prone. Any engine can build sludge if not taken care of correctly. But, to get to your actual question the MMO probably knocked some crude loose causing your drop in pressure. How long have you been driving with it in the oil and how much did you put in?

 

What oil are you running? And the Motorcraft filters are ok but they aren't on the same level and Wix/Napa Gold or Mobil 1

 

The guy I got it from did not take care of it at all so I'm trying to get her back to life I put 16oz of mmo and I'm running rotela 10-30. And I only been driving about 100 miles so far.

 

If your drop in pressure continues I would change the oil again. Not sure how far you are into your current oil cycle but it could help drain out whatever crude was knocked loose. I don't think you really have much to worry about though. Just keep up on the oil changes and use a good filter, I'd stick with the Rotella as well. You can continue to use the MMO if you like, but I wouldn't go overboard with it. I personally only use it once a year.

 

The extra detergents in Rotella will help clean up some of the crap in the engine from previous neglect. It's all I will put in my Jeeps.

As for the oil pressure, keep an eye on it. It should stabilize out after a tank of gas or two as some of that crap in the engine gets dissolved.

 

I have to agree with xjsnake. I have never like to put any additive in and as long as you keep up you maintenance you shouldn't have to. All I use is Rotella and ever since then I haven't had any problems with any build up. If you pressure seem to keep dropping take off the oil sending unit and see if the hole didn't get plugged up with all of the crud. Just be careful when you pull it off they can be damaged pretty easy.

 

And where is the oil sending unit located at.

 

Right by the oil filter. If I use any additive I will run a quart or so of trans fluid in a cruddy engine for about 10 min then drain and fill with oil. I run 15W40 rotella cause its free to me

 

It also happens to be the magic elixir for these engines

 

No kidding. Rotella 15-40 and Wix/Napa Gold filters go together like peas and carrots. Ask Forrest gump. He'll tell ya.

Throw a quart of MMO in and see it clean up even more quickly.