what break in oil/standard oil combo would you use for a 4.0

[stamina]

new piston rings are going to be installed here soon as well as some other bottom end things, what break in oil would you guys use for this?

 

[dvdswan]

Preferences are going to vary. Break in oil is only needed until oil pressure is at normal psi. That being said, it is very important to prime the oil pressure. (So I've been told by an old drag racer).

I've always used STP oil treatment, I've never had an issue. I've built 6 engines and they have all lasted over 250k. Take your time, get your clearances close and proper torque settings, and be sure parts are clean before installing.

 

[rubydist]

You want the cheapest dino oil you can find for break in oil. The new synthetics and semi-synthetics are so slippery that the rings don't want to break in correctly. The whole purpose of break in oil is to get the rings to seat.

Where you live the synthetic Walmart oil is perfectly fine. I've done uoa on that after 5k miles and it still was going strong. I just switched back to Mobil1 on mine because sometimes it gets cold enough in the winter that the Walmart stuff is thicker than I like, and the Mobil1 does not get that thick when its cold in my experience. Mobil1 is a little more expensive but I know from testing that I can run it 10k miles.

 

[Northidahotrailblazer]

I hope your doing cam bearings on your rebuild also. If you don't you will still have a lifter tick. Just a heads up.

 

[stamina]

You want the cheapest dino oil you can find for break in oil. The new synthetics and semi-synthetics are so slippery that the rings don't want to break in correctly. The whole purpose of break in oil is to get the rings to seat.

Where you live the synthetic Walmart oil is perfectly fine. I've done uoa on that after 5k miles and it still was going strong. I just switched back to Mobil1 on mine because sometimes it gets cold enough in the winter that the Walmart stuff is thicker than I like, and the Mobil1 does not get that thick when its cold in my experience. Mobil1 is a little more expensive but I know from testing that I can run it 10k miles.

do you use only break in oil? or do you do a mix?

 

[Angie]

" Preferences are going to vary. " <<< I agree

For my tear downs and rebuilds, it comes done to how long the engine will be sitting before being fired. remember that after the engine is turned off, most oil will recede to the pan eventually. If the tear down build is a few days to a couple weeks, i will just soak all parts in regular 10-30 and slap her together and fire it up. because the oil will shoot to pressure very fast after a few revolutions of the oil pump. (if not, you have bigger issues)

With computer controlled engines all the perimeters are set for you, so you don't need to be fully worried about out of time, hotter, colder, firing of the timing to mar the rings on any break ins. Most damage can be done during the settings of timing during an initial "1st" firing of a rebuild. IE, carbed and distributor. Myself, I just run a normal oil for 10-15 minutes to set the rings on any 4L I re-do. try to keep the RPM's above 1500 - 2000

Flat tappet engines require a different break in then a roller system will. I lube all stuff in pre-break in lube, then after a 20-25 minute fire up change the oil and filter to rid of the "gunky" oil and add new.

as said above, every one will add a different slice to this pie.... cheers

 

[rubydist]

I just use cheap regular oil for the break in period.

I use STP for assembly lube - that is what I smear on everything (bearings, cams, thrust washers, cylinder walls) during assembly. It stays on way better than oil so its not metal on metal those first few hundred revolutions at initial startup. The oil from the oil pump washes it off and mixes it with the oil for the break in period. And I try to crank the engine without spark until the oil pressure comes up during that initial startup.