So background on jeep is 1350000 miles hairline crack in head. Bone stock.. So as iv been trying to change oil every 1500 miles to hopefully buy me time till I either get head replaced or whatever I'm gonna do.. I've been running 10-30 with fram ultra gaurd..
Decided to go with a lil heavier weight oil and better filter so went with 10-40 and mopar filter. Well it used to make a light knocking up until it warmed up then went away, ever since I switched over its constantly there but goes away as soon as I give it gas?? Tried tightening flex plate bolts,checked for cracks, used higher octane gas, draining a quart and adding one of Lucas and nothing. The sound is loudest at the bottom of oil pan "close to the drain plug. In case I can't upload video it sounds like someone is under my jeep just barely tapping with a tiny wood hammer it speeds up a little bit when I first give it gas but as soon as rpms start to go up its gone or I can't hear it one sorry for the novel..any ideas http://https://youtu.be/fflU1Dd22Mk BTW oil does not get milky but psi IS under spec 10 when HOT, have not confirmed with mech gauge psi builds to about 36@2000 rpms

 

Sounds like the oil is too thick and the pump can't move enough oil unless the rpms are up a bit. I would go back to 10-30. The sound could easily go away.

 

My thoughts also, I'll be changing it soon. lol.. is 10-40 really that much thicker

 

If you have a weak oil pump which can happen with age it can be.

 

Could not stand wondering any longer went to Walmart got oil changed it out and no more knock!!! Makes me wonder if mabey I should change the pump I'm gonna go ahead and order the head now that I don't have a knock ..gonna verify oil pso with gauge also hopefully my bearings are fine after all . either way I can find out when I drop the pan

 

BTW went with mobile 5-30 figured lower cold viscosity would help get oil up top faster.

 

I believe that's what the manual reccomends for cold weather. I use delo 400 10-30 cuz I'm crazy about oil. It comes for working at a fuel/oil distributor for a while.

 

Yeah but its 95 degrees in ga right now. I'm just Happy I can sleep tonight, I swear I could hear that knocking in my sleep "shudders"

 

10w30 always. Don't try and add thicker oil.